QPair class is a template class that stores a pair of items. 更多...
| 头： | #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 & other ) |
| QPair & | operator= (const QPair<TT1, TT2> & p ) |
| QPair & | 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 ) |
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 = 3.14159265358979323846;
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
first
and
second
:
struct Variable { QString name; double value; }; Variable v; v.name = "pi"; v.value = 3.14159265358979323846;
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 assignable data types . You cannot, for example, store a QWidget as a value; instead, store a QWidget *. A few functions have additional requirements; these requirements are documented on a per-function basis.
另请参阅 容器类 .
The type of the first element in the pair (T1).
另请参阅 first .
The type of the second element in the pair (T2).
另请参阅 second .
Constructs an empty pair. The
first
and
second
elements are initialized with
默认构造值
s.
Constructs a pair and initializes the
first
element with
value1
和
second
element with
value2
.
另请参阅 qMakePair ().
Constructs a pair from the other pair
p
, of types TT1 and TT2. This constructor will fail if
first
cannot be initialized from
p.first
or if
second
cannot be initialized from
p.second
.
该函数在 Qt 5.2 引入。
另请参阅 qMakePair ().
移动构造 QPair instance, making it point to the same object that p 所指向的。
该函数在 Qt 5.2 引入。
Swaps this pair with other .
相当于
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
.
该函数在 Qt 5.5 引入。
Copies pair p into this pair.
该函数在 Qt 5.2 引入。
另请参阅 qMakePair ().
Move-assigns pair p into this pair instance.
该函数在 Qt 5.2 引入。
The first element in the pair.
The second element in the pair.
返回 QPair <T1, T2> that contains value1 and value2 。范例：
QList<QPair<int, double> > list; list.append(qMakePair(66, 3.14159));
这相当于 QPair <T1, T2>( value1 , value2 ), but usually requires less typing.
这是重载函数。
交换 lhs with rhs .
该函数在 Qt 5.5 引入。
返回
true
if
p1
不等于
p2
; otherwise returns false. Two pairs compare as not equal if their
first
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==()
.
返回
true
if
p1
is less than
p2
; otherwise returns false. The comparison is done on the
first
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<()
.
Writes the pair pair 到流 out .
This function requires the T1 and T2 types to implement
operator<<()
.
另请参阅 序列化 Qt 数据类型 .
返回
true
if
p1
小于等于
p2
；否则返回
false
. The comparison is done on the
first
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<()
.
返回
true
if
p1
等于
p2
；否则返回
false
. Two pairs compare equal if their
first
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==()
.
返回
true
if
p1
大于
p2
; otherwise returns false. The comparison is done on the
first
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<()
.
返回
true
if
p1
is greater than or equal to
p2
；否则返回
false
. The comparison is done on the
first
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<()
.
Reads a pair from stream in into pair .
This function requires the T1 and T2 types to implement
operator>>()
.
另请参阅 序列化 Qt 数据类型 .
