QVector 类

template <typename T> class QVector

QVector 类是提供动态数组的模板类。更多...

头：	#include <QVector>
qmake:	QT += core
继承者：	QPolygon , QPolygonF , QStack , QVulkanInfoVector ，和 QXmlStreamAttributes

所有成员列表，包括继承成员

注意： 此类的所有函数可重入 .

公共类型

typedef	ConstIterator
typedef	Iterator
typedef	const_iterator
typedef	const_pointer
typedef	const_reference
typedef	const_reverse_iterator
typedef	difference_type
typedef	iterator
typedef	pointer
typedef	reference
typedef	reverse_iterator
typedef	size_type
typedef	value_type

公共函数

	QVector (InputIterator first , InputIterator last )
	QVector (std::initializer_list<T> args )
	QVector (QVector<T> && other )
	QVector (const QVector<T> & other )
	QVector (int size , const T & value )
	QVector (int size )
	QVector ()
QVector<T> &	operator= (QVector<T> && other )
QVector<T> &	operator= (const QVector<T> & other )
	~QVector ()
void	append (const T & value )
void	append (T && value )
void	append (const QVector<T> & value )
const T &	at (int i ) const
QVector::reference	back ()
QVector::const_reference	back () const
QVector::iterator	begin ()
QVector::const_iterator	begin () const
int	capacity () const
QVector::const_iterator	cbegin () const
QVector::const_iterator	cend () const
void	clear ()
QVector::const_iterator	constBegin () const
const T *	constData () const
QVector::const_iterator	constEnd () const
const T &	constFirst () const
const T &	constLast () const
bool	contains (const T & value ) const
int	count (const T & value ) const
int	count () const
QVector::const_reverse_iterator	crbegin () const
QVector::const_reverse_iterator	crend () const
T *	data ()
const T *	data () const
bool	empty () const
QVector::iterator	end ()
QVector::const_iterator	end () const
bool	endsWith (const T & value ) const
QVector::iterator	erase (QVector::iterator pos )
QVector::iterator	erase (QVector::iterator begin , QVector::iterator end )
QVector<T> &	fill (const T & value , int size = -1)
T &	first ()
const T &	first () const
T &	front ()
QVector::const_reference	front () const
int	indexOf (const T & value , int from = 0) const
void	insert (int i , T && value )
void	insert (int i , const T & value )
void	insert (int i , int count , const T & value )
QVector::iterator	insert (QVector::iterator before , int count , const T & value )
QVector::iterator	insert (QVector::iterator before , const T & value )
QVector::iterator	insert (QVector::iterator before , T && value )
bool	isEmpty () const
T &	last ()
const T &	last () const
int	lastIndexOf (const T & value , int from = -1) const
int	length () const
QVector<T>	mid (int pos , int length = -1) const
void	move (int from , int to )
void	pop_back ()
void	pop_front ()
void	prepend (T && value )
void	prepend (const T & value )
void	push_back (const T & value )
void	push_back (T && value )
void	push_front (T && value )
void	push_front (const T & value )
QVector::reverse_iterator	rbegin ()
QVector::const_reverse_iterator	rbegin () const
void	remove (int i )
void	remove (int i , int count )
int	removeAll (const T & t )
void	removeAt (int i )
void	removeFirst ()
void	removeLast ()
bool	removeOne (const T & t )
QVector::reverse_iterator	rend ()
QVector::const_reverse_iterator	rend () const
void	replace (int i , const T & value )
void	reserve (int size )
void	resize (int size )
void	shrink_to_fit ()
int	size () const
void	squeeze ()
bool	startsWith (const T & value ) const
void	swap (QVector<T> & other )
void	swapItemsAt (int i , int j )
T	takeAt (int i )
T	takeFirst ()
T	takeLast ()
QList<T>	toList () const
std::vector<T>	toStdVector () const
T	value (int i ) const
T	value (int i , const T & defaultValue ) const
bool	operator!= (const QVector<T> & other ) const
QVector<T>	operator+ (const QVector<T> & other ) const
QVector<T> &	operator+= (const QVector<T> & other )
QVector<T> &	operator+= (const T & value )
QVector<T> &	operator+= (T && value )
QVector<T> &	operator<< (const T & value )
QVector<T> &	operator<< (const QVector<T> & other )
QVector<T> &	operator<< (T && value )
QVector<T> &	operator= (std::initializer_list<T> args )
bool	operator== (const QVector<T> & other ) const
T &	operator[] (int i )
const T &	operator[] (int i ) const

静态公共成员

QVector<T>	fromList (const QList<T> & list )
QVector<T>	fromStdVector (const std::vector<T> & vector )

uint	qHash (const QVector<T> & key , uint seed = 0)
bool	operator< (const QVector<T> & lhs , const QVector<T> & rhs )
QDataStream &	operator<< (QDataStream & out , const QVector<T> & vector )
bool	operator<= (const QVector<T> & lhs , const QVector<T> & rhs )
bool	operator> (const QVector<T> & lhs , const QVector<T> & rhs )
bool	operator>= (const QVector<T> & lhs , const QVector<T> & rhs )
QDataStream &	operator>> (QDataStream & in , QVector<T> & vector )

详细描述

QVector<T> 是一种 Qt 一般容器类。它将项存储在相邻内存位置，并提供基于索引的快速访问。

QList <T>, QLinkedList<T>, QVector<T>，和 QVarLengthArray <T> 提供类似 API 和功能。它们经常可互换，但有性能后果。这里是用例概述：

QVector should be your default first choice. QVector<T> will usually give better performance than QList <T>, because QVector<T> always stores its items sequentially in memory, where QList <T> will allocate its items on the heap unless sizeof(T) <= sizeof(void*) and T has been declared to be either a Q_MOVABLE_TYPE 或 Q_PRIMITIVE_TYPE 使用 Q_DECLARE_TYPEINFO 。见 Pros and Cons of Using QList for an explanation.
不管怎样， QList is used throughout the Qt APIs for passing parameters and for returning values. Use QList to interface with those APIs.
If you need a real linked list, which guarantees 常量时间 insertions mid-list and uses iterators to items rather than indexes, use QLinkedList.

注意： QVector 和 QVarLengthArray 两者均保证兼容 C 数组布局。 QList 不。这可能很重要，若应用程序必须接口 C API。

注意： Iterators into a QLinkedList and references into heap-allocating QLists remain valid as long as the referenced items remain in the container. This is not true for iterators and references into a QVector and non-heap-allocating QLists.

Here's an example of a QVector that stores integers and a QVector that stores QString 值：

QVector<int> integerVector;
QVector<QString> stringVector;

QVector stores its items in a vector (array). Typically, vectors are created with an initial size. For example, the following code constructs a QVector with 200 elements:

QVector<QString> vector(200);

The elements are automatically initialized with a 默认构造值 . If you want to initialize the vector with a different value, pass that value as the second argument to the constructor:

QVector<QString> vector(200, "Pass");

You can also call fill () at any time to fill the vector with a value.

QVector uses 0-based indexes, just like C++ arrays. To access the item at a particular index position, you can use operator[](). On non-const vectors, operator[]() returns a reference to the item that can be used on the left side of an assignment:

if (vector[0] == "Liz")
    vector[0] = "Elizabeth";

For read-only access, an alternative syntax is to use at ():

for (int i = 0; i < vector.size(); ++i) {
    if (vector.at(i) == "Alfonso")
        cout << "Found Alfonso at position " << i << Qt::endl;
}

at () can be faster than operator[](), because it never causes a 深拷贝的出现。

Another way to access the data stored in a QVector is to call data (). The function returns a pointer to the first item in the vector. You can use the pointer to directly access and modify the elements stored in the vector. The pointer is also useful if you need to pass a QVector to a function that accepts a plain C++ array.

If you want to find all occurrences of a particular value in a vector, use indexOf () 或 lastIndexOf (). The former searches forward starting from a given index position, the latter searches backward. Both return the index of the matching item if they found one; otherwise, they return -1. For example:

int i = vector.indexOf("Harumi");
if (i != -1)
    cout << "First occurrence of Harumi is at position " << i << Qt::endl;

If you simply want to check whether a vector contains a particular value, use contains (). If you want to find out how many times a particular value occurs in the vector, use count ().

QVector provides these basic functions to add, move, and remove items: insert (), replace (), remove (), prepend (), append (). With the exception of append () 和 replace (), these functions can be slow ( 线性时间 ) for large vectors, because they require moving many items in the vector by one position in memory. If you want a container class that provides fast insertion/removal in the middle, use QList or QLinkedList instead.

Unlike plain C++ arrays, QVectors can be resized at any time by calling resize (). If the new size is larger than the old size, QVector might need to reallocate the whole vector. QVector tries to reduce the number of reallocations by preallocating up to twice as much memory as the actual data needs.

If you know in advance approximately how many items the QVector will contain, you can call reserve (), asking QVector to preallocate a certain amount of memory. You can also call capacity () to find out how much memory QVector actually allocated.

Note that using non-const operators and functions can cause QVector to do a deep copy of the data. This is due to 隐式共享 .

QVector's value type must be an 可赋值数据类型 . This covers most data types that are commonly used, but the compiler won't let you, for example, store a QWidget 作为值；取而代之，存储 QWidget *. A few functions have additional requirements; for example, indexOf () 和 lastIndexOf () expect the value type to support operator==() . These requirements are documented on a per-function basis.

Like the other container classes, QVector provides Java 风格迭代器 ( QVectorIterator and QMutableVectorIterator ) 和 STL 样式迭代器 ( QVector::const_iterator and QVector::iterator ). In practice, these are rarely used, because you can use indexes into the QVector.

In addition to QVector, Qt also provides QVarLengthArray ，具有小的功能速度优化的很低级类。

QVector does not support inserting, prepending, appending or replacing with references to its own values. Doing so will cause your application to abort with an error message.

有关使用 Qt 容器的更多信息

有关比较 Qt 各种容器和 STL 容器的详细讨论，见理解 Qt 容器 .

最大尺寸和内存不足情况

The current version of QVector is limited to just under 2 GB (2^31 bytes) in size. The exact value is architecture-dependent, since it depends on the overhead required for managing the data block, but is no more than 32 bytes. The number of elements that can be stored in a QVector is that size divided by the size of each element.

In case memory allocation fails, QVector will use the Q_CHECK_PTR macro, which will throw a std::bad_alloc exception if the application is being compiled with exception support. If exceptions are disabled, then running out of memory is undefined behavior.

Note that the operating system may impose further limits on applications holding a lot of allocated memory, especially large, contiguous blocks. Such considerations, the configuration of such behavior or any mitigation are outside the scope of the Qt API.

另请参阅 QVectorIterator , QMutableVectorIterator , QList ，和 QLinkedList .

成员类型文档编制

typedef QVector:: ConstIterator

Qt 样式同义词 QVector::const_iterator .

typedef QVector:: Iterator

Qt 样式同义词 QVector::iterator .

typedef QVector:: const_iterator

The QVector::const_iterator typedef provides an STL-style const iterator for QVector and QStack .

QVector provides both STL 样式迭代器 and Java 风格迭代器 . The STL-style const iterator is simply a typedef for "const T *" (pointer to const T).

警告： Iterators on implicitly shared containers do not work exactly like STL-iterators. You should avoid copying a container while iterators are active on that container. For more information, read 隐式共享迭代器问题 .

另请参阅 QVector::constBegin (), QVector::constEnd (), QVector::iterator ，和 QVectorIterator .

typedef QVector:: const_pointer

Typedef for const T *. Provided for STL compatibility.

typedef QVector:: const_reference

Typedef for T &. Provided for STL compatibility.

typedef QVector:: const_reverse_iterator

The QVector::const_reverse_iterator typedef provides an STL-style const reverse iterator for QVector .

It is simply a typedef for std::reverse_iterator<const T*> .

该 typedef 在 Qt 5.6 引入。

另请参阅 QVector::rbegin (), QVector::rend (), QVector::reverse_iterator ，和 QVector::const_iterator .

typedef QVector:: difference_type

typedef 对于 ptrdiff_t。为兼容 STL 提供。

typedef QVector:: iterator

The QVector::iterator typedef provides an STL-style non-const iterator for QVector and QStack .

QVector provides both STL 样式迭代器 and Java 风格迭代器 . The STL-style non-const iterator is simply a typedef for "T *" (pointer to T).

另请参阅 QVector::begin (), QVector::end (), QVector::const_iterator ，和 QMutableVectorIterator .

typedef QVector:: pointer

Typedef for T *. Provided for STL compatibility.

typedef QVector:: reference

Typedef for T &. Provided for STL compatibility.

typedef QVector:: reverse_iterator

The QVector::reverse_iterator typedef provides an STL-style non-const reverse iterator for QVector .

It is simply a typedef for std::reverse_iterator<T*> .

该 typedef 在 Qt 5.6 引入。

另请参阅 QVector::rbegin (), QVector::rend (), QVector::const_reverse_iterator ，和 QVector::iterator .

typedef QVector:: size_type

typedef 对于 int。为兼容 STL 提供。

typedef QVector:: value_type

typedef 对于 T。为兼容 STL 提供。

成员函数文档编制

void QVector:: push_front ( T && value )

void QVector:: push_front (const T & value )

This function is provided for STL compatibility. It is equivalent to prepend( value ).

QVector::iterator QVector:: insert ( QVector::iterator before , T && value )

QVector::iterator QVector:: insert ( QVector::iterator before , const T & value )

这是重载函数。

插入 value in front of the item pointed to by the iterator before . Returns an iterator pointing at the inserted item.

void QVector:: insert ( int i , T && value )

void QVector:: insert ( int i , const T & value )

插入 value at index position i in the vector. If i is 0, the value is prepended to the vector. If i is size (), the value is appended to the vector.

范例：

QVector<QString> vector;
vector << "alpha" << "beta" << "delta";
vector.insert(2, "gamma");
// vector: ["alpha", "beta", "gamma", "delta"]

For large vectors, this operation can be slow ( 线性时间 ), because it requires moving all the items at indexes i and above by one position further in memory. If you want a container class that provides a fast insert () function, use QLinkedList instead.

另请参阅 append (), prepend ()，和 remove ().

void QVector:: prepend ( T && value )

void QVector:: prepend (const T & value )

插入 value at the beginning of the vector.

范例：

QVector<QString> vector;
vector.prepend("one");
vector.prepend("two");
vector.prepend("three");
// vector: ["three", "two", "one"]

This is the same as vector.insert(0, value ).

For large vectors, this operation can be slow ( 线性时间 ), because it requires moving all the items in the vector by one position further in memory. If you want a container class that provides a fast prepend () function, use QList or QLinkedList instead.

另请参阅 append () 和 insert ().

template <typename InputIterator> QVector:: QVector ( InputIterator first , InputIterator last )

Constructs a vector with the contents in the iterator range [ first , last ).

The value type of InputIterator must be convertible to T .

该函数在 Qt 5.14 引入。

QVector:: QVector ( std::initializer_list < T > args )

Constructs a vector from the std::initializer_list given by args .

This constructor is only enabled if the compiler supports C++11 initializer lists.

该函数在 Qt 4.8 引入。

QVector:: QVector ( QVector < T > && other )

Move-constructs a QVector instance, making it point at the same object that other 所指向的。

该函数在 Qt 5.2 引入。

QVector:: QVector (const QVector < T > & other )

构造副本为 other .

此操作花费常量时间 , because QVector is 隐式共享 . This makes returning a QVector from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and that takes 线性时间 .

另请参阅 operator= ().

QVector:: QVector ( int size , const T & value )

Constructs a vector with an initial size of size elements. Each element is initialized with value .

另请参阅 resize () 和 fill ().

QVector:: QVector ( int size )

Constructs a vector with an initial size of size 元素。

元素被初始化采用默认构造值 .

另请参阅 resize ().

QVector:: QVector ()

Constructs an empty vector.

另请参阅 resize ().

QVector < T > &QVector:: operator= ( QVector < T > && other )

移动赋值 other 到此 QVector 实例。

该函数在 Qt 5.2 引入。

QVector < T > &QVector:: operator= (const QVector < T > & other )

赋值 other to this vector and returns a reference to this vector.

QVector:: ~QVector ()

Destroys the vector.

void QVector:: append (const T & value )

插入 value at the end of the vector.

范例：

QVector<QString> vector;
vector.append("one");
vector.append("two");
QString three = "three";
vector.append(three);
// vector: ["one", "two", "three"]
// three: "three"

This is the same as calling resize( size () + 1) and assigning value to the new last element in the vector.

This operation is relatively fast, because QVector typically allocates more memory than necessary, so it can grow without reallocating the entire vector each time.

另请参阅 operator<< (), prepend ()，和 insert ().

void QVector:: append ( T && value )

这是重载函数。

范例：

QVector<QString> vector;
vector.append("one");
vector.append("two");
QString three = "three";
vector.append(std::move(three));
// vector: ["one", "two", "three"]
// three: ""

该函数在 Qt 5.6 引入。

void QVector:: append (const QVector < T > & value )

这是重载函数。

Appends the items of the value vector to this vector.

该函数在 Qt 5.5 引入。

另请参阅 operator<< () 和 operator+= ().

const T &QVector:: at ( int i ) const

返回项按索引位置 i in the vector.

i must be a valid index position in the vector (i.e., 0 <= i < size ()).

另请参阅 value () 和 operator[] ().

QVector::reference QVector:: back ()

此函数为兼容 STL (标准模板库) 提供。它相当于 last ().

QVector::const_reference QVector:: back () const

这是重载函数。

QVector::iterator QVector:: begin ()

返回 STL 样式迭代器 pointing to the first item in the vector.

另请参阅 constBegin () 和 end ().

QVector::const_iterator QVector:: begin () const

这是重载函数。

int QVector:: capacity () const

Returns the maximum number of items that can be stored in the vector without forcing a reallocation.

The sole purpose of this function is to provide a means of fine tuning QVector 's memory usage. In general, you will rarely ever need to call this function. If you want to know how many items are in the vector, call size ().

另请参阅 reserve () 和 squeeze ().

QVector::const_iterator QVector:: cbegin () const

返回常量 STL 样式迭代器 pointing to the first item in the vector.

该函数在 Qt 5.0 引入。

另请参阅 begin () 和 cend ().

QVector::const_iterator QVector:: cend () const

返回常量 STL 样式迭代器 pointing to the imaginary item after the last item in the vector.

该函数在 Qt 5.0 引入。

另请参阅 cbegin () 和 end ().

void QVector:: clear ()

Removes all the elements from the vector.

注意： Until Qt 5.6, this also released the memory used by the vector. From Qt 5.7, the capacity is preserved. To shed all capacity, swap with a default-constructed vector:

QVector<T> v ...;
QVector<T>().swap(v);
Q_ASSERT(v.capacity() == 0);

or call squeeze ().

另请参阅 squeeze ().

QVector::const_iterator QVector:: constBegin () const

返回常量 STL 样式迭代器 pointing to the first item in the vector.

另请参阅 begin () 和 constEnd ().

const T *QVector:: constData () const

Returns a const pointer to the data stored in the vector. The pointer can be used to access the items in the vector. The pointer remains valid as long as the vector isn't reallocated.

This function is mostly useful to pass a vector to a function that accepts a plain C++ array.

另请参阅 data () 和 operator[] ().

QVector::const_iterator QVector:: constEnd () const

返回常量 STL 样式迭代器 pointing to the imaginary item after the last item in the vector.

另请参阅 constBegin () 和 end ().

const T &QVector:: constFirst () const

Returns a const reference to the first item in the vector. This function assumes that the vector isn't empty.

该函数在 Qt 5.6 引入。

另请参阅 constLast (), isEmpty ()，和 first ().

const T &QVector:: constLast () const

Returns a const reference to the last item in the vector. This function assumes that the vector isn't empty.

该函数在 Qt 5.6 引入。

另请参阅 constFirst (), isEmpty ()，和 last ().

bool QVector:: contains (const T & value ) const

返回 true if the vector contains an occurrence of value ；否则返回 false .

This function requires the value type to have an implementation of operator==() .

另请参阅 indexOf () 和 count ().

int QVector:: count (const T & value ) const

Returns the number of occurrences of value in the vector.

This function requires the value type to have an implementation of operator==() .

另请参阅 contains () 和 indexOf ().

int QVector:: count () const

这是重载函数。

如同 size ().

QVector::const_reverse_iterator QVector:: crbegin () const

返回常量 STL-style reverse iterator pointing to the first item in the vector, in reverse order.

该函数在 Qt 5.6 引入。

另请参阅 begin (), rbegin ()，和 rend ().

QVector::const_reverse_iterator QVector:: crend () const

返回常量 STL-style reverse iterator pointing to one past the last item in the vector, in reverse order.

该函数在 Qt 5.6 引入。

另请参阅 end (), rend ()，和 rbegin ().

T *QVector:: data ()

Returns a pointer to the data stored in the vector. The pointer can be used to access and modify the items in the vector.

范例：

QVector<int> vector(10);
int *data = vector.data();
for (int i = 0; i < 10; ++i)
    data[i] = 2 * i;

The pointer remains valid as long as the vector isn't reallocated.

This function is mostly useful to pass a vector to a function that accepts a plain C++ array.

另请参阅 constData () 和 operator[] ().

const T *QVector:: data () const

这是重载函数。

bool QVector:: empty () const

此函数为兼容 STL (标准模板库) 提供。它相当于 isEmpty (), returning true if the vector is empty; otherwise returns false .

QVector::iterator QVector:: end ()

返回 STL 样式迭代器 pointing to the imaginary item after the last item in the vector.

另请参阅 begin () 和 constEnd ().

QVector::const_iterator QVector:: end () const

这是重载函数。

bool QVector:: endsWith (const T & value ) const

返回 true if this vector is not empty and its last item is equal to value ；否则返回 false .

该函数在 Qt 4.5 引入。

另请参阅 isEmpty () 和 last ().

QVector::iterator QVector:: erase ( QVector::iterator pos )

Removes the item pointed to by the iterator pos from the vector, and returns an iterator to the next item in the vector (which may be end ()).

另请参阅 insert () 和 remove ().

QVector::iterator QVector:: erase ( QVector::iterator begin , QVector::iterator end )

这是重载函数。

Removes all the items from begin up to (but not including) end . Returns an iterator to the same item that end referred to before the call.

QVector < T > &QVector:: fill (const T & value , int size = -1)

赋值 value to all items in the vector. If size is different from -1 (the default), the vector is resized to size size 事先。

范例：

QVector<QString> vector(3);
vector.fill("Yes");
// vector: ["Yes", "Yes", "Yes"]
vector.fill("oh", 5);
// vector: ["oh", "oh", "oh", "oh", "oh"]

另请参阅 resize ().

T &QVector:: first ()

Returns a reference to the first item in the vector. This function assumes that the vector isn't empty.

另请参阅 last (), isEmpty ()，和 constFirst ().

const T &QVector:: first () const

这是重载函数。

`[static]` QVector < T > QVector:: fromList (const QList < T > & list )

返回 QVector object with the data contained in list .

范例：

QStringList list;
list << "Sven" << "Kim" << "Ola";
QVector<QString> vect = QVector<QString>::fromList(list);
// vect: ["Sven", "Kim", "Ola"]

注意： Since Qt 5.14, range constructors are available for Qt's generic 容器类 and should be used in place of this method.

另请参阅 toList () 和 QList::toVector ().

`[static]` QVector < T > QVector:: fromStdVector (const std::vector < T > & vector )

返回 QVector object with the data contained in vector . The order of the elements in the QVector is the same as in vector .

范例：

std::vector<double> stdvector;
vector.push_back(1.2);
vector.push_back(0.5);
vector.push_back(3.14);
QVector<double> vector = QVector<double>::fromStdVector(stdvector);

注意： Since Qt 5.14, range constructors are available for Qt's generic 容器类 and should be used in place of this method.

另请参阅 toStdVector () 和 QList::fromStdList ().

T &QVector:: front ()

此函数为兼容 STL (标准模板库) 提供。它相当于 first ().

QVector::const_reference QVector:: front () const

这是重载函数。

int QVector:: indexOf (const T & value , int from = 0) const

Returns the index position of the first occurrence of value in the vector, searching forward from index position from . Returns -1 if no item matched.

范例：

QVector<QString> vector;
vector << "A" << "B" << "C" << "B" << "A";
vector.indexOf("B");            // returns 1
vector.indexOf("B", 1);         // returns 1
vector.indexOf("B", 2);         // returns 3
vector.indexOf("X");            // returns -1

This function requires the value type to have an implementation of operator==() .

另请参阅 lastIndexOf () 和 contains ().

void QVector:: insert ( int i , int count , const T & value )

这是重载函数。

插入 count 个副本对于 value at index position i in the vector.

范例：

QVector<double> vector;
vector << 2.718 << 1.442 << 0.4342;
vector.insert(1, 3, 9.9);
// vector: [2.718, 9.9, 9.9, 9.9, 1.442, 0.4342]

QVector::iterator QVector:: insert ( QVector::iterator before , int count , const T & value )

插入 count 个副本对于 value in front of the item pointed to by the iterator before . Returns an iterator pointing at the first of the inserted items.

bool QVector:: isEmpty () const

返回 true if the vector has size 0; otherwise returns false .

另请参阅 size () 和 resize ().

T &QVector:: last ()

Returns a reference to the last item in the vector. This function assumes that the vector isn't empty.

另请参阅 first (), isEmpty ()，和 constLast ().

const T &QVector:: last () const

这是重载函数。

int QVector:: lastIndexOf (const T & value , int from = -1) const

Returns the index position of the last occurrence of the value value in the vector, searching backward from index position from 。若 from is -1 (the default), the search starts at the last item. Returns -1 if no item matched.

范例：

QList<QString> vector;
vector << "A" << "B" << "C" << "B" << "A";
vector.lastIndexOf("B");        // returns 3
vector.lastIndexOf("B", 3);     // returns 3
vector.lastIndexOf("B", 2);     // returns 1
vector.lastIndexOf("X");        // returns -1

This function requires the value type to have an implementation of operator==() .

另请参阅 indexOf ().

int QVector:: length () const

如同 size () 和 count ().

Provided for compatibility with QList .

该函数在 Qt 5.2 引入。

另请参阅 size (), count ()，和 QList::length ().

QVector < T > QVector:: mid ( int pos , int length = -1) const

Returns a sub-vector which contains elements from this vector, starting at position pos 。若 length is -1 (the default), all elements after pos are included; otherwise length elements (or all remaining elements if there are less than length elements) are included.

void QVector:: move ( int from , int to )

移动项按索引位置 from 到索引位置 to .

Provided for compatibility with QList .

该函数在 Qt 5.6 引入。

另请参阅 QList::move ().

void QVector:: pop_back ()

此函数为兼容 STL (标准模板库) 提供。它相当于 removeLast ().

void QVector:: pop_front ()

此函数为兼容 STL (标准模板库) 提供。它相当于 removeFirst ().

void QVector:: push_back (const T & value )

This function is provided for STL compatibility. It is equivalent to append( value ).

void QVector:: push_back ( T && value )

这是重载函数。

该函数在 Qt 5.6 引入。

QVector::reverse_iterator QVector:: rbegin ()

返回 STL-style reverse iterator pointing to the first item in the vector, in reverse order.

该函数在 Qt 5.6 引入。

另请参阅 begin (), crbegin ()，和 rend ().

QVector::const_reverse_iterator QVector:: rbegin () const

这是重载函数。

该函数在 Qt 5.6 引入。

void QVector:: remove ( int i )

这是重载函数。

Removes the element at index position i .

另请参阅 insert (), replace ()，和 fill ().

void QVector:: remove ( int i , int count )

这是重载函数。

移除 count elements from the middle of the vector, starting at index position i .

另请参阅 insert (), replace ()，和 fill ().

int QVector:: removeAll (const T & t )

Removes all elements that compare equal to t from the vector. Returns the number of elements removed, if any.

Provided for compatibility with QList .

该函数在 Qt 5.4 引入。

另请参阅 removeOne () 和 QList::removeAll ().

void QVector:: removeAt ( int i )

Removes the element at index position i . Equivalent to

remove(i);

Provided for compatibility with QList .

该函数在 Qt 5.2 引入。

另请参阅 remove () 和 QList::removeAt ().

void QVector:: removeFirst ()

Removes the first item in the vector. Calling this function is equivalent to calling remove(0). The vector must not be empty. If the vector can be empty, call isEmpty () before calling this function.

该函数在 Qt 5.1 引入。

另请参阅 remove (), takeFirst ()，和 isEmpty ().

void QVector:: removeLast ()

Removes the last item in the vector. Calling this function is equivalent to calling remove( size () - 1). The vector must not be empty. If the vector can be empty, call isEmpty () before calling this function.

该函数在 Qt 5.1 引入。

另请参阅 remove (), takeLast (), removeFirst ()，和 isEmpty ().

bool QVector:: removeOne (const T & t )

Removes the first element that compares equal to t from the vector. Returns whether an element was, in fact, removed.

Provided for compatibility with QList .

该函数在 Qt 5.4 引入。

另请参阅 removeAll () 和 QList::removeOne ().

QVector::reverse_iterator QVector:: rend ()

返回 STL-style reverse iterator pointing to one past the last item in the vector, in reverse order.

该函数在 Qt 5.6 引入。

另请参阅 end (), crend ()，和 rbegin ().

QVector::const_reverse_iterator QVector:: rend () const

这是重载函数。

该函数在 Qt 5.6 引入。

void QVector:: replace ( int i , const T & value )

替换项在索引位置 i with value .

i must be a valid index position in the vector (i.e., 0 <= i < size ()).

另请参阅 operator[] () 和 remove ().

void QVector:: reserve ( int size )

试图分配内存为至少 size elements. If you know in advance how large the vector will be, you should call this function to prevent reallocations and memory fragmentation.

若 size is an underestimate, the worst that will happen is that the QVector will be a bit slower. If size is an overestimate, you may have used more memory than the normal QVector growth strategy would have allocated—or you may have used less.

An alternative to reserve() is calling resize (). Whether or not that is faster than reserve() depends on the element type, because resize () default-constructs all elements, and requires assignment to existing entries rather than calling append (), which copy- or move-constructs. For simple types, like int or double , resize () is typically faster, but for anything more complex, you should prefer reserve().

警告： If the size passed to resize () was underestimated, you run out of allocated space and into undefined behavior. This problem does not exist with reserve(), because it treats the size as just a hint.

另请参阅 squeeze () 和 capacity ().

void QVector:: resize ( int size )

Sets the size of the vector to size 。若 size is greater than the current size, elements are added to the end; the new elements are initialized with a 默认构造值。若 size is less than the current size, elements are removed from the end.

Since Qt 5.6, resize() doesn't shrink the capacity anymore. To shed excess capacity, use squeeze ().

另请参阅 size ().

void QVector:: shrink_to_fit ()

此函数为兼容 STL (标准模板库) 提供。它相当于 squeeze ().

该函数在 Qt 5.10 引入。

int QVector:: size () const

Returns the number of items in the vector.

另请参阅 isEmpty () 和 resize ().

void QVector:: squeeze ()

Releases any memory not required to store the items.

The sole purpose of this function is to provide a means of fine tuning QVector 's memory usage. In general, you will rarely ever need to call this function.

另请参阅 reserve () 和 capacity ().

bool QVector:: startsWith (const T & value ) const

返回 true if this vector is not empty and its first item is equal to value ；否则返回 false .

该函数在 Qt 4.5 引入。

另请参阅 isEmpty () 和 first ().

void QVector:: swap ( QVector < T > & other )

Swaps vector other with this vector. This operation is very fast and never fails.

该函数在 Qt 4.8 引入。

void QVector:: swapItemsAt ( int i , int j )

Exchange the item at index position i with the item at index position j . This function assumes that both i and j are at least 0 but less than size (). To avoid failure, test that both i and j are at least 0 and less than size ().

该函数在 Qt 5.14 引入。

T QVector:: takeAt ( int i )

Removes the element at index position i and returns it.

相当于

T t = at(i);
remove(i);
return t;

Provided for compatibility with QList .

该函数在 Qt 5.2 引入。

另请参阅 takeFirst (), takeLast ()，和 QList::takeAt ().

T QVector:: takeFirst ()

Removes the first item in the vector and returns it. This function assumes the vector is not empty. To avoid failure, call isEmpty () before calling this function.

该函数在 Qt 5.1 引入。

另请参阅 takeLast () 和 removeFirst ().

T QVector:: takeLast ()

Removes the last item in the list and returns it. This function assumes the vector is not empty. To avoid failure, call isEmpty () before calling this function.

若不使用返回值， removeLast () 效率更高。

该函数在 Qt 5.1 引入。

另请参阅 takeFirst () 和 removeLast ().

QList < T > QVector:: toList () const

返回 QList object with the data contained in this QVector .

范例：

QVector<QString> vect;
vect << "red" << "green" << "blue" << "black";
QList<QString> list = vect.toList();
// list: ["red", "green", "blue", "black"]

注意： Since Qt 5.14, range constructors are available for Qt's generic 容器类 and should be used in place of this method.

另请参阅 fromList () 和 QList::fromVector ().

std::vector < T > QVector:: toStdVector () const

Returns a std::vector object with the data contained in this QVector 。范例：

QVector<double> vector;
vector << 1.2 << 0.5 << 3.14;
std::vector<double> stdvector = vector.toStdVector();

注意： Since Qt 5.14, range constructors are available for Qt's generic 容器类 and should be used in place of this method.

另请参阅 fromStdVector () 和 QList::toStdList ().

T QVector:: value ( int i ) const

Returns the value at index position i in the vector.

If the index i is out of bounds, the function returns a 默认构造值 . If you are certain that i is within bounds, you can use at () instead, which is slightly faster.

另请参阅 at () 和 operator[] ().

T QVector:: value ( int i , const T & defaultValue ) const

这是重载函数。

If the index i is out of bounds, the function returns defaultValue .

bool QVector:: operator!= (const QVector < T > & other ) const

返回 true if other is not equal to this vector; otherwise returns false .

Two vectors are considered equal if they contain the same values in the same order.

This function requires the value type to have an implementation of operator==() .

另请参阅 operator== ().

QVector < T > QVector:: operator+ (const QVector < T > & other ) const

Returns a vector that contains all the items in this vector followed by all the items in the other vector.

另请参阅 operator+= ().

QVector < T > &QVector:: operator+= (const QVector < T > & other )

Appends the items of the other vector to this vector and returns a reference to this vector.

另请参阅 operator+ () 和 append ().

QVector < T > &QVector:: operator+= (const T & value )

这是重载函数。

追加 value to the vector.

另请参阅 append () 和 operator<< ().

QVector < T > &QVector:: operator+= ( T && value )

这是重载函数。

该函数在 Qt 5.11 引入。

另请参阅 append () 和 operator<< ().

QVector < T > &QVector:: operator<< (const T & value )

追加 value to the vector and returns a reference to this vector.

另请参阅 append () 和 operator+= ().

QVector < T > &QVector:: operator<< (const QVector < T > & other )

追加 other to the vector and returns a reference to the vector.

QVector < T > &QVector:: operator<< ( T && value )

这是重载函数。

该函数在 Qt 5.11 引入。

另请参阅 append () 和 operator+= ().

QVector < T > &QVector:: operator= ( std::initializer_list < T > args )

Assigns the collection of values in args 到此 QVector 实例。

This operator is only enabled if the compiler supports C++11 initializer lists.

该函数在 Qt 5.14 引入。

bool QVector:: operator== (const QVector < T > & other ) const

返回 true if other is equal to this vector; otherwise returns false .

Two vectors are considered equal if they contain the same values in the same order.

This function requires the value type to have an implementation of operator==() .

另请参阅 operator!= ().

T &QVector:: operator[] ( int i )

返回项按索引位置 i 作为可修改引用。

i must be a valid index position in the vector (i.e., 0 <= i < size ()).

Note that using non-const operators can cause QVector to do a deep copy.

另请参阅 at () 和 value ().

const T &QVector:: operator[] ( int i ) const

这是重载函数。

如同 at( i ).

QVector 类

公共类型

公共函数

静态公共成员

相关非成员

详细描述

有关使用 Qt 容器的更多信息

最大尺寸和内存不足情况

成员类型文档编制

typedef QVector:: ConstIterator

typedef QVector:: Iterator

typedef QVector:: const_iterator

typedef QVector:: const_pointer

typedef QVector:: const_reference

typedef QVector:: const_reverse_iterator

typedef QVector:: difference_type

typedef QVector:: iterator

typedef QVector:: pointer

typedef QVector:: reference

typedef QVector:: reverse_iterator

typedef QVector:: size_type

typedef QVector:: value_type

成员函数文档编制

void QVector:: push_front ( T && value )

void QVector:: push_front (const T & value )

QVector::iterator QVector:: insert ( QVector::iterator before , T && value )

QVector::iterator QVector:: insert ( QVector::iterator before , const T & value )

void QVector:: insert ( int i , T && value )

void QVector:: insert ( int i , const T & value )

void QVector:: prepend ( T && value )

void QVector:: prepend (const T & value )

template <typename InputIterator> QVector:: QVector ( InputIterator first , InputIterator last )

QVector:: QVector ( std::initializer_list < T > args )

QVector:: QVector ( QVector < T > && other )

QVector:: QVector (const QVector < T > & other )

QVector:: QVector ( int size , const T & value )

QVector:: QVector ( int size )

QVector:: QVector ()

QVector < T > &QVector:: operator= ( QVector < T > && other )

QVector < T > &QVector:: operator= (const QVector < T > & other )

QVector:: ~QVector ()

void QVector:: append (const T & value )

void QVector:: append ( T && value )

void QVector:: append (const QVector < T > & value )

const T &QVector:: at ( int i ) const

QVector::reference QVector:: back ()

QVector::const_reference QVector:: back () const

QVector::iterator QVector:: begin ()

QVector::const_iterator QVector:: begin () const

int QVector:: capacity () const

QVector::const_iterator QVector:: cbegin () const

QVector::const_iterator QVector:: cend () const

void QVector:: clear ()

QVector::const_iterator QVector:: constBegin () const

const T *QVector:: constData () const

QVector::const_iterator QVector:: constEnd () const

const T &QVector:: constFirst () const

const T &QVector:: constLast () const

bool QVector:: contains (const T & value ) const

int QVector:: count (const T & value ) const

int QVector:: count () const

QVector::const_reverse_iterator QVector:: crbegin () const

QVector::const_reverse_iterator QVector:: crend () const

T *QVector:: data ()

const T *QVector:: data () const

bool QVector:: empty () const

QVector::iterator QVector:: end ()

QVector::const_iterator QVector:: end () const

bool QVector:: endsWith (const T & value ) const

QVector::iterator QVector:: erase ( QVector::iterator pos )

QVector::iterator QVector:: erase ( QVector::iterator begin , QVector::iterator end )

QVector < T > &QVector:: fill (const T & value , int size = -1)

T &QVector:: first ()

const T &QVector:: first () const

[static] QVector < T > QVector:: fromList (const QList < T > & list )

[static] QVector < T > QVector:: fromStdVector (const std::vector < T > & vector )

T &QVector:: front ()

QVector::const_reference QVector:: front () const

int QVector:: indexOf (const T & value , int from = 0) const

void QVector:: insert ( int i , int count , const T & value )

`[static]` QVector < T > QVector:: fromList (const QList < T > & list )

`[static]` QVector < T > QVector:: fromStdVector (const std::vector < T > & vector )