QVarLengthArray 類 供低級可變長度數組。 更多...
| 頭： | #include <QVarLengthArray> |
| qmake: | QT += core |
注意： 此類的所有函數 可重入 .
| 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 |
| QVarLengthArray (InputIterator first , InputIterator last ) | |
| QVarLengthArray (std::initializer_list<T> args ) | |
| QVarLengthArray (const QVarLengthArray<T, Prealloc> & other = Prealloc) | |
| QVarLengthArray (int size ) | |
| QVarLengthArray () | |
| QVarLengthArray<T, Prealloc> & | operator= (const QVarLengthArray<T, Prealloc> & other = Prealloc) |
| ~QVarLengthArray () | |
| void | append (const T & t ) |
| void | append (T && t ) |
| void | append (const T * buf , int size ) |
| const T & | at (int i ) const |
| T & | back () |
| const T & | back () const |
| QVarLengthArray::iterator | begin () |
| QVarLengthArray::const_iterator | begin () const |
| int | capacity () const |
| QVarLengthArray::const_iterator | cbegin () const |
| QVarLengthArray::const_iterator | cend () const |
| void | clear () |
| QVarLengthArray::const_iterator | constBegin () const |
| const T * | constData () const |
| QVarLengthArray::const_iterator | constEnd () const |
| bool | contains (const T & value ) const |
| int | count () const |
| QVarLengthArray::const_reverse_iterator | crbegin () const |
| QVarLengthArray::const_reverse_iterator | crend () const |
| T * | data () |
| const T * | data () const |
| bool | empty () const |
| QVarLengthArray::iterator | end () |
| QVarLengthArray::const_iterator | end () const |
| QVarLengthArray::iterator | erase (QVarLengthArray::const_iterator pos ) |
| QVarLengthArray::iterator | erase (QVarLengthArray::const_iterator begin , QVarLengthArray::const_iterator end ) |
| T & | first () |
| const T & | first () const |
| T & | front () |
| const T & | 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 ) |
| QVarLengthArray::iterator | insert (QVarLengthArray::const_iterator before , int count , const T & value ) |
| QVarLengthArray::iterator | insert (QVarLengthArray::const_iterator before , T && value ) |
| QVarLengthArray::iterator | insert (QVarLengthArray::const_iterator before , const T & value ) |
| bool | isEmpty () const |
| T & | last () |
| const T & | last () const |
| int | lastIndexOf (const T & value , int from = -1) const |
| int | length () const |
| void | pop_back () |
| void | prepend (T && value ) |
| void | prepend (const T & value ) |
| void | push_back (const T & t ) |
| void | push_back (T && t ) |
| QVarLengthArray::reverse_iterator | rbegin () |
| QVarLengthArray::const_reverse_iterator | rbegin () const |
| void | remove (int i ) |
| void | remove (int i , int count ) |
| void | removeLast () |
| QVarLengthArray::reverse_iterator | rend () |
| QVarLengthArray::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 () |
| T | value (int i ) const |
| T | value (int i , const T & defaultValue ) const |
| QVarLengthArray<T, Prealloc> & | operator+= (const T & value ) |
| QVarLengthArray<T, Prealloc> & | operator+= (T && value ) |
| QVarLengthArray<T, Prealloc> & | operator<< (const T & value ) |
| QVarLengthArray<T, Prealloc> & | operator<< (T && value ) |
| QVarLengthArray<T, Prealloc> & | operator= (std::initializer_list<T> list ) |
| T & | operator[] (int i ) |
| const T & | operator[] (int i ) const |
| uint | qHash (const QVarLengthArray<T, Prealloc> & key = Prealloc, uint seed = 0) |
| bool | operator!= (const QVarLengthArray<T, Prealloc1> & left = Prealloc1, const QVarLengthArray<T, Prealloc2> & right = Prealloc2) |
| bool | operator< (const QVarLengthArray<T, Prealloc1> & lhs = Prealloc1, const QVarLengthArray<T, Prealloc2> & rhs = Prealloc2) |
| bool | operator<= (const QVarLengthArray<T, Prealloc1> & lhs = Prealloc1, const QVarLengthArray<T, Prealloc2> & rhs = Prealloc2) |
| bool | operator== (const QVarLengthArray<T, Prealloc1> & left = Prealloc1, const QVarLengthArray<T, Prealloc2> & right = Prealloc2) |
| bool | operator> (const QVarLengthArray<T, Prealloc1> & lhs = Prealloc1, const QVarLengthArray<T, Prealloc2> & rhs = Prealloc2) |
| bool | operator>= (const QVarLengthArray<T, Prealloc1> & lhs = Prealloc1, const QVarLengthArray<T, Prealloc2> & rhs = Prealloc2) |
The C++ language doesn't support variable-length arrays on the stack. For example, the following code won't compile:
int myfunc(int n) { int table[n + 1]; // WRONG ... return table[n]; }
The alternative is to allocate the array on the heap (with
new
):
int myfunc(int n) { int *table = new int[n + 1]; ... int ret = table[n]; delete[] table; return ret; }
However, if myfunc() is called very frequently from the application's inner loop, heap allocation can be a major source of slowdown.
QVarLengthArray is an attempt to work around this gap in the C++ language. It allocates a certain number of elements on the stack, and if you resize the array to a larger size, it automatically uses the heap instead. Stack allocation has the advantage that it is much faster than heap allocation.
範例：
int myfunc(int n) { QVarLengthArray<int, 1024> array(n + 1); ... return array[n]; }
In the example above, QVarLengthArray will preallocate 1024 elements on the stack and use them unless
n + 1
is greater than 1024. If you omit the second template argument, QVarLengthArray's default of 256 is used.
QVarLengthArry 的值類型必須是 可賦值數據類型 . This covers most data types that are commonly used, but the compiler won't let you, for example, store a QWidget 作為值；取而代之，存儲 QWidget *.
QVarLengthArray，像 QVector , provides a resizable array data structure. The main differences between the two classes are:
In summary, QVarLengthArray is a low-level optimization class that only makes sense in very specific cases. It is used a few places inside Qt and was added to Qt's public API for the convenience of advanced users.
另請參閱 QVector , QList ，和 QLinkedList .
Typedef for const T *. Provided for STL compatibility.
This typedef was introduced in Qt 4.7.
Typedef for const T *. Provided for STL compatibility.
This typedef was introduced in Qt 4.7.
Typedef for const T &. Provided for STL compatibility.
This typedef was introduced in Qt 4.7.
typedef 對於
std::reverse_iterator<const T*>
. Provided for STL compatibility.
該 typedef 在 Qt 5.6 引入。
typedef 對於 ptrdiff_t。為兼容 STL 提供。
This typedef was introduced in Qt 4.7.
Typedef for T *. Provided for STL compatibility.
This typedef was introduced in Qt 4.7.
Typedef for T *. Provided for STL compatibility.
This typedef was introduced in Qt 4.7.
Typedef for T &. Provided for STL compatibility.
This typedef was introduced in Qt 4.7.
typedef 對於
std::reverse_iterator<T*>
. Provided for STL compatibility.
該 typedef 在 Qt 5.6 引入。
typedef 對於 int。為兼容 STL 提供。
This typedef was introduced in Qt 4.7.
typedef 對於 T。為兼容 STL 提供。
This typedef was introduced in Qt 4.7.
這是重載函數。
插入 value in front of the item pointed to by the iterator before . Returns an iterator pointing at the inserted item.
該函數在 Qt 4.8 引入。
插入 value at index position i in the array. If i is 0, the value is prepended to the vector. If i is size (), the value is appended to the vector.
For large arrays, this operation can be slow ( 綫性時間 ), 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.
該函數在 Qt 4.8 引入。
另請參閱 remove ().
插入 value at the beginning of the array.
This is the same as vector.insert(0, value ).
For large arrays, this operation can be slow ( 綫性時間 ), 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.
該函數在 Qt 4.8 引入。
Constructs an array with the contents in the iterator range [ first , last ).
The value type of
InputIterator
must be convertible to
T
.
該函數在 Qt 5.14 引入。
Constructs an array from the std::initializer_list given by args .
該函數在 Qt 5.5 引入。
構造副本為 other .
Constructs an array with an initial size of size 元素。
If the value type is a primitive type (e.g., char, int, float) or a pointer type (e.g., QWidget *), the elements are not initialized. For other types, the elements are initialized with a 默認構造值 .
Constructs an array with an initial size of zero.
賦值 other to this array and returns a reference to this array.
Destroys the array.
Appends item t to the array, extending the array if necessary.
另請參閱 removeLast ().
This function overloads append.
注意：
Unlike the lvalue overload of append(), passing a reference to an object that is already an element of
*this
leads to undefined behavior:
vla.append(std::move(vla[0])); // BUG: passing an object that is already in the container
該函數在 Qt 5.9 引入。
追加 size amount of items referenced by buf 到此數組。
Returns a reference to the item at index position i .
i must be a valid index position in the array (i.e., 0 <= i < size ()).
另請參閱 value () 和 operator[] ().
如同 last (). Provided for STL-compatibility.
該函數在 Qt 5.0 引入。
這是重載函數。
該函數在 Qt 5.0 引入。
返迴 STL 樣式迭代器 pointing to the first item in the array.
該函數在 Qt 4.8 引入。
另請參閱 constBegin () 和 end ().
這是重載函數。
該函數在 Qt 4.8 引入。
Returns the maximum number of elements that can be stored in the array without forcing a reallocation.
The sole purpose of this function is to provide a means of fine tuning QVarLengthArray '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 array, call size ().
返迴常量 STL 樣式迭代器 pointing to the first item in the array.
該函數在 Qt 5.0 引入。
返迴常量 STL 樣式迭代器 pointing to the imaginary item after the last item in the array.
該函數在 Qt 5.0 引入。
Removes all the elements from the array.
Same as resize(0).
返迴常量 STL 樣式迭代器 pointing to the first item in the array.
該函數在 Qt 4.8 引入。
Returns a const pointer to the data stored in the array. The pointer can be used to access the items in the array. The pointer remains valid as long as the array isn't reallocated.
This function is mostly useful to pass an array to a function that accepts a plain C++ array.
另請參閱 data () 和 operator[] ().
返迴常量 STL 樣式迭代器 pointing to the imaginary item after the last item in the array.
該函數在 Qt 4.8 引入。
另請參閱 constBegin () 和 end ().
返迴
true
if the array contains an occurrence of
value
；否則返迴
false
.
This function requires the value type to have an implementation of
operator==()
.
該函數在 Qt 5.3 引入。
另請參閱 indexOf () 和 lastIndexOf ().
如同 size ().
返迴常量 STL-style reverse iterator pointing to the first item in the variable length array, in reverse order.
該函數在 Qt 5.6 引入。
另請參閱 begin (), rbegin ()，和 rend ().
返迴常量 STL-style reverse iterator pointing to one past the last item in the variable length array, in reverse order.
該函數在 Qt 5.6 引入。
另請參閱 end (), rend ()，和 rbegin ().
Returns a pointer to the data stored in the array. The pointer can be used to access and modify the items in the array.
範例：
QVarLengthArray<int> array(10); int *data = array.data(); for (int i = 0; i < 10; ++i) data[i] = 2 * i;
The pointer remains valid as long as the array isn't reallocated.
This function is mostly useful to pass an array to a function that accepts a plain C++ array.
另請參閱 constData () 和 operator[] ().
這是重載函數。
返迴
true
if the array has size 0; otherwise returns
false
.
如同 isEmpty (). Provided for STL-compatibility.
該函數在 Qt 5.0 引入。
返迴 STL 樣式迭代器 pointing to the imaginary item after the last item in the array.
該函數在 Qt 4.8 引入。
這是重載函數。
該函數在 Qt 4.8 引入。
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 ()).
該函數在 Qt 4.8 引入。
這是重載函數。
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.
該函數在 Qt 4.8 引入。
Returns a reference to the first item in the array. The array must not be empty. If the array can be empty, check isEmpty () before calling this function.
這是重載函數。
如同 first (). Provided for STL-compatibility.
該函數在 Qt 5.0 引入。
這是重載函數。
該函數在 Qt 5.0 引入。
Returns the index position of the first occurrence of value in the array, searching forward from index position from . Returns -1 if no item matched.
This function requires the value type to have an implementation of
operator==()
.
該函數在 Qt 5.3 引入。
另請參閱 lastIndexOf () 和 contains ().
這是重載函數。
插入 count 個副本對於 value at index position i in the vector.
該函數在 Qt 4.8 引入。
插入 count 個副本對於 value in front of the item pointed to by the iterator before . Returns an iterator pointing at the first of the inserted items.
該函數在 Qt 4.8 引入。
返迴
true
if the array has size 0; otherwise returns
false
.
Returns a reference to the last item in the array. The array must not be empty. If the array can be empty, check isEmpty () before calling this function.
這是重載函數。
Returns the index position of the last occurrence of the value value in the array, 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.
This function requires the value type to have an implementation of
operator==()
.
該函數在 Qt 5.3 引入。
另請參閱 indexOf () 和 contains ().
如同 size ().
該函數在 Qt 5.0 引入。
如同 removeLast (). Provided for STL-compatibility.
該函數在 Qt 5.0 引入。
Appends item t to the array, extending the array if necessary. Provided for STL-compatibility.
該函數在 Qt 5.0 引入。
This function overloads push_back.
注意：
Unlike the lvalue overload of push_back(), passing a reference to an object that is already an element of
*this
leads to undefined behavior:
vla.push_back(std::move(vla[0])); // BUG: passing an object that is already in the container
該函數在 Qt 5.9 引入。
返迴 STL-style reverse iterator pointing to the first item in the variable length array, in reverse order.
該函數在 Qt 5.6 引入。
另請參閱 begin (), crbegin ()，和 rend ().
這是重載函數。
該函數在 Qt 5.6 引入。
這是重載函數。
Removes the element at index position i .
該函數在 Qt 4.8 引入。
這是重載函數。
移除 count elements from the middle of the array, starting at index position i .
該函數在 Qt 4.8 引入。
Decreases the size of the array by one. The allocated size is not changed.
該函數在 Qt 4.5 引入。
另請參閱 append ().
返迴 STL-style reverse iterator pointing to one past the last item in the variable length array, in reverse order.
該函數在 Qt 5.6 引入。
另請參閱 end (), crend ()，和 rbegin ().
這是重載函數。
該函數在 Qt 5.6 引入。
替換項在索引位置 i with value .
i must be a valid index position in the array (i.e., 0 <= i < size ()).
該函數在 Qt 4.8 引入。
另請參閱 operator[] () 和 remove ().
試圖分配內存為至少 size elements. If you know in advance how large the array can get, you can call this function and if you call resize () often, you are likely to get better performance. If size is an underestimate, the worst that will happen is that the QVarLengthArray will be a bit slower.
The sole purpose of this function is to provide a means of fine tuning QVarLengthArray 's memory usage. In general, you will rarely ever need to call this function. If you want to change the size of the array, call resize ().
另請參閱 capacity () 和 squeeze ().
Sets the size of the array to size 。若 size is greater than the current size, elements are added to the end. If size is less than the current size, elements are removed from the end.
If the value type is a primitive type (e.g., char, int, float) or a pointer type (e.g., QWidget *), new elements are not initialized. For other types, the elements are initialized with a 默認構造值 .
如同 squeeze (). Provided for STL-compatibility.
該函數在 Qt 5.10 引入。
Returns the number of elements in the array.
Releases any memory not required to store the items. If the container can fit its storage on the stack allocation, it will free the heap allocation and copy the elements back to the stack.
The sole purpose of this function is to provide a means of fine tuning QVarLengthArray 's memory usage. In general, you will rarely ever need to call this function.
該函數在 Qt 5.1 引入。
另請參閱 reserve (), capacity ()，和 resize ().
Returns the value at index position i .
If the index i is out of bounds, the function returns a 默認構造值 . If you are certain that i is within bounds, you can use at () instead, which is slightly faster.
另請參閱 at () 和 operator[] ().
這是重載函數。
If the index i is out of bounds, the function returns defaultValue .
追加 value to the array and returns a reference to this vector.
該函數在 Qt 4.8 引入。
另請參閱 append () 和 operator<< ().
這是重載函數。
該函數在 Qt 5.11 引入。
另請參閱 append () 和 operator<< ().
追加 value to the array and returns a reference to this vector.
該函數在 Qt 4.8 引入。
另請參閱 append () 和 operator+= ().
這是重載函數。
該函數在 Qt 5.11 引入。
另請參閱 append () 和 operator+= ().
Assigns the values of list to this array, and returns a reference to this array.
該函數在 Qt 5.5 引入。
Returns a reference to the item at index position i .
i must be a valid index position in the array (i.e., 0 <= i < size ()).
這是重載函數。
返迴哈希值為 key ，使用 seed 做計算種子。
該函數在 Qt 5.14 引入。
返迴
true
if the two arrays, specified by
left
and
right
, are
not
equal.
Two arrays 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==()
.
該函數在 Qt 4.8 引入。
另請參閱 operator== ().
返迴
true
if variable length array
lhs
is
lexicographically less than
rhs
；否則返迴
false
.
This function requires the value type to have an implementation of
operator<()
.
該函數在 Qt 5.6 引入。
返迴
true
if variable length array
lhs
is
lexicographically less than or equal to
rhs
；否則返迴
false
.
This function requires the value type to have an implementation of
operator<()
.
該函數在 Qt 5.6 引入。
返迴
true
if the two arrays, specified by
left
and
right
, are equal.
Two arrays 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==()
.
該函數在 Qt 4.8 引入。
另請參閱 operator!= ().
返迴
true
if variable length array
lhs
is
lexicographically greater than
rhs
；否則返迴
false
.
This function requires the value type to have an implementation of
operator<()
.
該函數在 Qt 5.6 引入。
返迴
true
if variable length array
lhs
is
lexicographically greater than or equal to
rhs
；否則返迴
false
.
This function requires the value type to have an implementation of
operator<()
.
該函數在 Qt 5.6 引入。
