c – 如何在QList中使用qSort和自定义类型？

我在排序包含结构实例的QList时遇到问题：

class modelHeuristic
{

    typedef struct {

         QString c;
         QString t;
         double value;
     }Saving;

public:

QList<Saving> list_saving;

#include "klarkeright.h"

klarkeRight::klarkeRight()
{


}
void klarkeRight::Algoritmo_Asimetrico(modelHeuristic *model)
{

    qSort(model->list_saving.begin(), model->list_saving.end());

}

error: invalid operands to binary expression (‘const modelHeuristic::Saving’ and ‘const modelHeuristic::Saving’)
return (t1 < t2);

解决方法:

首先,QtAlgorithms主要被弃用,你不应该使用它.请按照Qt文档的建议使用std::sort.

否则,您将需要实现实际的比较功能,因为您似乎正在使用自定义类型.当然,通用算法无法知道如何与这样的自定义项进行比较.这就是错误试图指出的.

然后,您需要将该函数作为第三个参数传递给排序算法,或者将其命名为operator<.我更喜欢明确,特别是从那以后你可以将你的比较限制在它所依赖的类中. 因此,我会写这样的东西： main.cpp中

#include <QtAlgorithms>
#include <QString>
#include <QList>

class modelHeuristic
{
    typedef struct {
        QString c;
        QString t;
        double value;
    } Saving;
    public:    
        static bool savingComparison(const Saving &s1, const Saving &s2)
        {
            return s1.value < s2.value; // This is just an example
        }

        QList<Saving> list_saving;
};

int main()
{
    modelHeuristic *model = new modelHeuristic();
    // This is not doing anything useful with an empty list
    // that is constructed, but it shows how to get the theory right!
    // Also, you really wish to use std::sort here instead.
    qSort(model->list_saving.begin(), model->list_saving.end(), modelHeuristic::savingComparison);
    return 0;
}

main.pro

TEMPLATE = app
TARGET = main
QT = core
SOURCES += main.cpp

构建并运行

qmake && make && ./main

有关详细信息,请参阅documentation.

标签：qtcore,qlist,c,sorting,qt
来源： https://codeday.me/bug/20190722/1505931.html