如何使用迭代器作为类成员向量？ [英] How do you use iterators for a class member vector?

问题描述

ostream & operator <<(ostream & os, LongNumber & along)
{

    for(std::vector<LongNumber>:: iterator i = (along.container).begin(); i != (along.container).end(); ++i) //this line give me errors
    {
        os << *i;
    }
      
    return os;
}

class LongNumber
{
    private:
        vector<int> number;

};

error: conversion from to non-scalar type iterator requested

error: no match for operator !=

i不知道出了什么问题。

i have no idea what's wrong.

推荐答案

在类中声明一个容器成员不会使该类成为容器，也不会为该类创建容器。



您的 LongNumber 类没有名为 container 的成员。你必须要写一个访问函数：

Declaring a container member in a class does not make the class a container, nor does it create a container for the class.

Your LongNumber class does not have a member called container. You have to either write an accessor function:

class LongNumber
{
    private:
        vector<int> number;
	public:
		vector<int>& container();
};

ostream & operator <<(ostream & os, LongNumber & along)
{
    for(std::vector<int>::iterator i = along.container().begin(); i != along.container().end(); ++i) 

或使其成为公共会员：

or make it a public member:

class LongNumber
{
	public:
        vector<int> number;
};

ostream & operator <<(ostream & os, LongNumber & along)
{
    for(std::vector<int>::iterator i = along.number.begin(); i != along.number.end(); ++i) 

或提供对开始和结束迭代器的访问：

or provide access to the beginning and end iterators:

class LongNumber
{
    private:
        vector<int> number;
	public:
		vector<int>::iterator begin()
		{    
		    return number.begin(); 
		}	
		vector<int>::const_iterator begin() const
		{    
			return number.begin(); 
		}	
		vector<int>::iterator end()
		{    
		    return number.end(); 
		}	
		vector<int>::const_iterator end() const
		{    
			return number.end(); 
		}	
};

ostream & operator <<(ostream & os, LongNumber & along)
{
    for(std::vector<int>::iterator i = along.begin(); i != along.end(); ++i) 

请注意，我已将循环中的类型从 std :: vector< LongNumber> 更改为 std :: vector< int> 此处。上面示例中的代码将遍历沿变量的成员容器的元素。

Note that I've changed the type in the loop from std::vector<LongNumber> to std::vector<int> here. The code in the examples above will iterate over the elements of the member container of your along variable.

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