# QPair

The QPair class is a template class that stores a pair of items. More...

` #include <QPair>`

## Public Types

typedef | first_type |

typedef | second_type |

## Public Functions

QPair () | |

QPair ( const T1 & value1, const T2 & value2 ) | |

QPair<T1, T2> & | operator= ( const QPair<T1, T2> & other ) |

## Public Variables

T1 | first |

T2 | second |

## Related Non-Members

QPair<T1, T2> | qMakePair ( const T1 & value1, const T2 & value2 ) |

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 ) |

## Detailed Description

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` value:

QPair<QString, double> pair;

The components are accessible as public data members called first and second. For example:

pair.first = "pi"; pair.second = 3.14159265358979323846;

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.

**See also **Container Classes.

## Member Type Documentation

### typedef QPair::first_type

The type of the first element in the pair (T1).

### typedef QPair::second_type

The type of the second element in the pair (T2).

## Member Function Documentation

### QPair::QPair ()

Constructs an empty pair. The `first` and `second` elements are initialized with default-constructed values.

### QPair::QPair ( const T1 & *value1*, const T2 & *value2* )

Constructs a pair and initializes the `first` element with *value1* and the `second` element with *value2*.

### QPair<T1, T2> & QPair::operator= ( const QPair<T1, T2> & *other* )

Assigns *other* to this pair.

## Member Variable Documentation

### T1 QPair::first

The first element in the pair.

### T2 QPair::second

The second element in the pair.

## Related Non-Members

### QPair<T1, T2> qMakePair ( const T1 & *value1*, const T2 & *value2* )

Returns a QPair<T1, T2> that contains *value1* and *value2*. Example:

QList<QPair<int, double> > list; list.append(qMakePair(66, 3.14159));

This is equivalent to QPair<T1, T2>(*value1*, *value2*), but usually requires less typing.

### bool operator!= ( const QPair<T1, T2> & *p1*, const QPair<T1, T2> & *p2* )

Returns true if *p1* is not equal to *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==()`.

### bool operator< ( const QPair<T1, T2> & *p1*, const QPair<T1, T2> & *p2* )

Returns 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<()`.

### QDataStream & operator<< ( QDataStream & *out*, const QPair<T1, T2> & *pair* )

Writes the pair *pair* to stream *out*.

This function requires the T1 and T2 types to implement `operator<<()`.

**See also **Serializing Qt Data Types.

### bool operator<= ( const QPair<T1, T2> & *p1*, const QPair<T1, T2> & *p2* )

Returns true if *p1* is less than or equal to *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<()`.

### bool operator== ( const QPair<T1, T2> & *p1*, const QPair<T1, T2> & *p2* )

Returns true if *p1* is equal to *p2*; otherwise returns 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==()`.

### bool operator> ( const QPair<T1, T2> & *p1*, const QPair<T1, T2> & *p2* )

Returns true if *p1* is greater 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<()`.

### bool operator>= ( const QPair<T1, T2> & *p1*, const QPair<T1, T2> & *p2* )

Returns true if *p1* is greater than or equal to *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<()`.

### QDataStream & operator>> ( QDataStream & *in*, QPair<T1, T2> & *pair* )

Reads a pair from stream *in* into *pair*.

This function requires the T1 and T2 types to implement `operator>>()`.

**See also **Serializing Qt Data Types.

© 2013 Digia Plc and/or its subsidiaries. Documentation contributions included herein are the copyrights of their respective owners.

The documentation provided herein is licensed under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation.

Documentation sources may be obtained from www.qt-project.org.

Digia, Qt and their respective logos are trademarks of Digia Plc in Finland and/or other countries worldwide. All other trademarks are property of their respective owners. Privacy Policy