問(wèn)題描述

嘗試編譯以下代碼時(shí)出現(xiàn)此編譯錯(cuò)誤，我該怎么辦?

trying to compile the following code I get this compile error, what can I do?

ISO C++ 禁止取地址不合格的或括號(hào)內(nèi)的非靜態(tài)成員函數(shù)形成一個(gè)指向成員函數(shù)的指針.

ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function to form a pointer to member function.

class MyClass {
   int * arr;
   // other member variables
   MyClass() { arr = new int[someSize]; }

   doCompare( const int & i1, const int & i2 ) { // use some member variables } 

   doSort() { std::sort(arr,arr+someSize, &doCompare); }

}; 

推薦答案

doCompare 必須是 static.如果 doCompare 需要來(lái)自 MyClass 的數(shù)據(jù)，您可以通過(guò)更改將 MyClass 變成一個(gè)比較函子:

doCompare must be static. If doCompare needs data from MyClass you could turn MyClass into a comparison functor by changing:

doCompare( const int & i1, const int & i2 ) { // use some member variables } 

進(jìn)入

bool operator () ( const int & i1, const int & i2 ) { // use some member variables } 

并調(diào)用:

doSort() { std::sort(arr, arr+someSize, *this); }

另外，doSort 是不是缺少返回值?

Also, isn't doSort missing a return value?

我認(rèn)為應(yīng)該可以使用 std::mem_fun 和某種綁定將成員函數(shù)轉(zhuǎn)換為自由函數(shù)，但目前我無(wú)法理解確切的語(yǔ)法.

I think it should be possible to use std::mem_fun and some sort of binding to turn the member function into a free function, but the exact syntax evades me at the moment.

Doh，std::sort 按值獲取函數(shù)，這可能是一個(gè)問(wèn)題.為了解決這個(gè)問(wèn)題，將函數(shù)包裝在類中:

Doh, std::sort takes the function by value which may be a problem. To get around this wrap the function inside the class:

class MyClass {
    struct Less {
        Less(const MyClass& c) : myClass(c) {}
        bool operator () ( const int & i1, const int & i2 ) {// use 'myClass'} 
        MyClass& myClass;
    };
    doSort() { std::sort(arr, arr+someSize, Less(*this)); }
}

這篇關(guān)于使用成員函數(shù)作為比較器進(jìn)行排序的問(wèn)題的文章就介紹到這了，希望我們推薦的答案對(duì)大家有所幫助，也希望大家多多支持html5模板網(wǎng)！