The QPair class is a template class that stores a pair of items. 更多...
| 頭： | #include <QPair> |
| qmake: | QT += core |
| typedef | first_type |
| typedef | second_type |
| QPair () | |
| QPair (const T1 & value1 , const T2 & value2 ) | |
| QPair (const QPair<TT1, TT2> & p ) | |
| QPair (QPair<TT1, TT2> && p ) | |
| void | swap (QPair<T1, T2> & other ) |
| QPair<T1, T2> & | operator= (const QPair<TT1, TT2> & p ) |
| QPair<T1, T2> & | operator= (QPair<TT1, TT2> && p ) |
| T1 | first |
| T2 | second |
| QPair<T1, T2> | qMakePair (const T1 & value1 , const T2 & value2 ) |
| void | swap (QPair<T1, T2> & lhs , QPair<T1, T2> & rhs ) |
| bool | operator!= (const QPair<T1, T2> & p1 , const QPair<T1, T2> & p2 ) |
| bool | operator< (const QPair<T1, T2> & p1 , const QPair<T1, T2> & p2 ) |
| QDataStream & | operator<< (QDataStream & out , const QPair<T1, T2> & pair ) |
| bool | operator<= (const QPair<T1, T2> & p1 , const QPair<T1, T2> & p2 ) |
| bool | operator== (const QPair<T1, T2> & p1 , const QPair<T1, T2> & p2 ) |
| bool | operator> (const QPair<T1, T2> & p1 , const QPair<T1, T2> & p2 ) |
| bool | operator>= (const QPair<T1, T2> & p1 , const QPair<T1, T2> & p2 ) |
| QDataStream & | operator>> (QDataStream & in , QPair<T1, T2> & pair ) |
The QPair class is a template class that stores a pair of items.
QPair
<T1, T2> can be used in your application if the STL
pair
type is not available. It stores one value of type T1 and one value of type T2. It can be used as a return value for a function that needs to return two values, or as the value type of a
generic container
.
Here's an example of a
QPair
that stores one
QString
and one
double
值：
QPair<QString, double> pair;
The components are accessible as public data members called first and second 。例如：
pair.first = "pi"; pair.second = M_PI;
Note, however, that it is almost always preferable to define a small struct to hold the result of a function with multiple return values. A struct trivially generalizes to more than two values, and allows more descriptive member names than
第一
and
second
:
struct Variable { QString name; double value; }; Variable v; v.name = "pi"; v.value = M_PI;
The advent of C++11 automatic variable type deduction (
auto
) shifts the emphasis from the type name to the name of functions and members. Thus,
QPair
, like
std::pair
and
std::tuple
, is mostly useful in generic (template) code, where defining a dedicated type is not possible.
QPair 's template data types (T1 and T2) must be 可賦值數據類型 。例如，無法存儲 QWidget 作為值；取而代之，存儲 QWidget *. A few functions have additional requirements; these requirements are documented on a per-function basis.
另請參閱 容器類 .
The type of the first element in the pair (T1).
另請參閱 first .
The type of the second element in the pair (T2).
另請參閱 second .
Constructs an empty pair. The
第一
and
second
elements are initialized with
默認構造值
。
Constructs a pair and initializes the
第一
element with
value1
和
second
element with
value2
.
另請參閱 qMakePair ().
Constructs a pair from the other pair
p
, of types TT1 and TT2. This constructor will fail if
第一
cannot be initialized from
p.first
or if
second
cannot be initialized from
p.second
.
該函數在 Qt 5.2 引入。
另請參閱 qMakePair ().
移動構造 QPair 實例，使它指嚮同一對象 p 所指嚮的。
該函數在 Qt 5.2 引入。
Swaps this pair with other .
相當於
qSwap(this->first, other.first); qSwap(this->second, other.second);
Swap overloads are found in namespace
std
as well as via argument-dependent lookup (ADL) in the namespace of
T
.
該函數在 Qt 5.5 引入。
Copies pair p into this pair.
該函數在 Qt 5.2 引入。
另請參閱 qMakePair ().
Move-assigns pair p into this pair instance.
該函數在 Qt 5.2 引入。
The first element in the pair.
The second element in the pair.
返迴 QPair <T1, T2> that contains value1 and value2 。範例：
QList<QPair<int, double> > list; list.append(qMakePair(66, M_PI));
這相當於 QPair <T1, T2>( value1 , value2 ), but usually requires less typing.
這是重載函數。
交換 lhs with rhs .
該函數在 Qt 5.5 引入。
返迴
true
if
p1
不等於
p2
; otherwise returns false. Two pairs compare as not equal if their
第一
data members are not equal or if their
second
data members are not equal.
This function requires the T1 and T2 types to have an implementation of
operator==()
.
返迴
true
if
p1
小於
p2
; otherwise returns false. The comparison is done on the
第一
members of
p1
and
p2
; if they compare equal, the
second
members are compared to break the tie.
This function requires the T1 and T2 types to have an implementation of
operator<()
.
寫入對 pair 到流 out .
此函數要求 T1 和 T2 類型以實現
operator<<()
.
另請參閱 序列化 Qt 數據類型 .
返迴
true
if
p1
<=
p2
；否則返迴
false
. The comparison is done on the
第一
members of
p1
and
p2
; if they compare equal, the
second
members are compared to break the tie.
This function requires the T1 and T2 types to have an implementation of
operator<()
.
返迴
true
if
p1
等於
p2
；否則返迴
false
. Two pairs compare equal if their
第一
data members compare equal and if their
second
data members compare equal.
This function requires the T1 and T2 types to have an implementation of
operator==()
.
返迴
true
if
p1
大於
p2
; otherwise returns false. The comparison is done on the
第一
members of
p1
and
p2
; if they compare equal, the
second
members are compared to break the tie.
This function requires the T1 and T2 types to have an implementation of
operator<()
.
返迴
true
if
p1
>=
p2
；否則返迴
false
. The comparison is done on the
第一
members of
p1
and
p2
; if they compare equal, the
second
members are compared to break the tie.
This function requires the T1 and T2 types to have an implementation of
operator<()
.
讀取對從流 in into pair .
此函數要求 T1 和 T2 類型以實現
operator>>()
.
另請參閱 序列化 Qt 數據類型 .
