使用STL find_if()在对象指针向量中查找特定对象

Question

我试图在对象指针的Vector中找到某个对象.让我们说这些是我的课程.

// Class.h
class Class{
public:
    int x;
    Class(int xx);
    bool operator==(const Class &other) const;
    bool operator<(const Class &other) const;
};

// Class.cpp
#include "Class.h"
Class::Class(int xx){
    x = xx;
}

bool Class::operator==(const Class &other) const {
    return (this->x == other.x);
}

bool Class::operator<(const Class &other) const {
    return (this->x < other.x);
}

// Main.cpp
#include <iostream>
#include <vector>
#include <algorithm>
#include "Class.h"
using namespace std;

int main(){
    vector<Class*> set;
    Class *c1 = new Class(55);
    Class *c2 = new Class(34);
    Class *c3 = new Class(67);
    set.push_back(c31);
    set.push_back(c32);
    set.push_back(c33);

    Class *c4 = new Class(34);
}

让我们说,就我的目的而言,如果它们的'x'值相同,则2个类的对象是相等的.所以在上面的代码中,我想在STL find_if()方法中使用谓词,以便能够在向量中"找到"c4.

我似乎无法使谓词起作用.我将查找谓词基于我为排序编写的谓词.

struct less{
    bool operator()(Class *c1, Class *c2){return  *c1 < *c2;}   
};
sort(set.begin(), set.end(), less());

这种排序谓词工作正常.所以我改编它用于寻找

struct eq{
    bool operator()(Class *c1, Class *c2){return  *c1 == *c2;}  
};

为什么这个谓词不起作用？为此编写谓词的更好方法是什么？

谢谢

Answer 1

find_if 采用一元谓词,而不是二元谓词.

struct eq{
    eq(const Class* compare_to) : compare_to_(compare_to) { }
    bool operator()(Class *c1) const {return  *c1 == *compare_to_;}  
private:
    const Class* compare_to_;
};

std::find_if(set.begin(), set.end(), eq(c4));