for_each用法-白红宇

for_each用法

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发布时间：2019-06-29

本文共 3022 字，大约阅读时间需要 10 分钟。

for_each()是个function template#include 
     
      头文件说明template
      
        inline    void _For_each(_InIt _First, _InIt _Last, _Fn1& _Func)    {    // perform function for each element    for (; _First != _Last; ++_First)        _Func(*_First);    }由以上source可知，for_each()只能配合global function和function object。#include 
       
        #include 
        
         #include "vector"#include "map"#include 
         
          #include 
          
           #include 
           
            using namespace std;//单一类对象class CClassObj{public: CClassObj(void){} ~CClassObj(void){} void PrintElem(){ std::cout << "mem_fun_ref" << std::endl; }};class ClassController{protected: vector
            
              _ObjVec;public: ClassController(void){} ~ClassController(void){} void AddClass(CClassObj cObj){ _ObjVec.push_back(cObj); } void PrintElem(){ for_each(_ObjVec.begin(), _ObjVec.end(), mem_fun_ref(&CClassObj::PrintElem)); }};//多态class AbstactClass{public: virtual void PrintElem(){ std::cout << "Abstact mem_fun 1" << std::endl; }};class MyClass1 : public AbstactClass{};class MyClass2 : public AbstactClass{public: void PrintElem(){ std::cout << "Abstact mem_fun 2" << std::endl; }};class ClassCont{protected: vector
             
               _ObjVec;public: void AddClass(AbstactClass& obj){ _ObjVec.push_back(&obj); } void PrintElem(){ for_each(_ObjVec.begin(), _ObjVec.end(), mem_fun(&AbstactClass::PrintElem)); }};struct Mystruct{ int cnt; string str; Mystruct() { cnt = 0; str = "str"; }};//函数调用对象 for_each()只能配合global function和function object。/*void Print(const Mystruct stru){ cout << stru.cnt << ", " << stru.str.c_str() << endl; }*/void Print(const Mystruct stru, const char* str){ cout << str << stru.cnt << ", " << stru.str.c_str() << endl; }struct PrintStru{ string _str = ""; PrintStru(string str) : _str(str){ } void operator()(string &str){ cout << _str.c_str() << str.c_str() << endl; }};int main(){/* Add a(1, 2), b(3, 4);*//* std::cout << a << " + " << b << " = " << (a + b) << std::endl;*/ vector
              
                vecStru; Mystruct stru; vecStru.push_back(stru); vecStru.push_back(stru); /*for_each(vecStru.begin(), vecStru.end(), [](const Mystruct stru){cout << stru.cnt << ", " << stru.str.c_str() << endl; });//lambda可调用对象*/ //Procedure Based與for_each()搭配 /*for_each(vecStru.begin(), vecStru.end(), Print);//print： 不传入参数*/ for_each(vecStru.begin(), vecStru.end(), bind2nd(ptr_fun(Print), "elem: "));//print： 传入参数 //Object Oriented與for_each()搭配 string Arr[] = { "123", "123456", "12345", "12", "1" }; vector
               
                 vecStr(Arr, Arr + sizeof(Arr) / sizeof(string)); for_each(vecStr.begin(), vecStr.end(), PrintStru(""));//print： 不传入参数 //若使用function object，也可以將參數傳給PrintStru()，透過constructor的技巧接收參數。 for_each(vecStr.begin(), vecStr.end(), PrintStru("Elem: "));//print： 不传入参数 ClassController cConT; cConT.AddClass(CClassObj()); cConT.AddClass(CClassObj()); cConT.PrintElem(); //多态 ClassCont cT; cT.AddClass(MyClass1()); cT.AddClass(MyClass2()); cT.PrintElem();}