转换QPair到QVariant [英] Convert QPair to QVariant

问题描述

我有以下问题:我想通过TCP传输数据，并为此编写了一个函数.为了获得最大的可重用性，功能模板为f(QPair<QString, QVariant> data).接收器将第一个值(也称为QString)用作目标地址，第二个值包含数据.现在我想传输一个QPair<int, int>值，但是不幸的是我无法将QPair转换为QVariant.最佳方法是能够传输一对int值而不必编写新函数(或使旧函数过载).在这种情况下，QPair的最佳替代方法是什么?

I have the following problem: I want to transmitt data via TCP, and wrote a function for that. For maximum reusability the function template is f(QPair<QString, QVariant> data). The first value (aka QString) is used by the receiver as target address, the second contains the data. Now I want to transfer a QPair<int, int>-value, but unfortunately I can not convert a QPair to a QVariant. The optimum would be to be able to transfer a pair of int-values without having to write a new function (or to overload the old one). What is the best alternative for QPair in this case?

推荐答案

您必须使用特殊的宏Q_DECLARE_METATYPE()使自定义类型可用于QVariant系统. 请仔细阅读文档以了解其工作原理.

You have to use the special macro Q_DECLARE_METATYPE() to make custom types available to QVariant system. Please read the doc carefully to understand how it works.

对于QPair而言，它非常简单:

For QPair though it's quite straightforward:

#include <QPair>
#include <QDebug>

typedef QPair<int,int> MyType;    // typedef for your type
Q_DECLARE_METATYPE(MyType);       // makes your type available to QMetaType system

int main(int argc, char *argv[])
{
    // ...

    MyType pair_in(1,2);
    QVariant variant = QVariant::fromValue(pair_in);
    MyType pair_out = variant.value<MyType>();
    qDebug() << pair_out;

    // ...
}

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