c ++初始化字符串指针数组 [英] c++ initialization of an array of string pointers

问题描述

我想初始化一个 std :: string 指针的大小，我从一个构造函数中获取的数组。另外，我想对两个 int 数组执行相同的操作，但是下面的代码不能编译：

I want to initialize an array of std::string pointers of size that i get from a constructor. Also, i want to do the same for two int arrays but the code below doesn't compile:

class MyQuickInitArray
{
public:
    MyQuickInitArray(int size)
    {
        if(size <= 0)
        {
            throw new std::exception;
        }

        _size = size;
        _counter = 0;
        A = new std::string[size];
        B = new int[size];
        C = new int[size];
    }

    std::string& operator[](int j) {
        if(j > _size)
        {
            throw std::out_of_range("out of range");
        }

        if(((B[j]<0) || (B[j]>=_counter)) || (C[B[j]]!=j))
        {
            // A[j] points to junk
            _counter++;
            A[j] = new std::string;
            B[j] = _counter-1;
            C[_counter-1] = j;
            return A[j];
        }

        // the cell was instantiated before
        return A[j];
    }

    ~MyQuickInitArray(){};


private:
    std::string* A[];
    int B[];
    int C[];
    int _size;
    int _counter;
};

如何正确地声明一个我从ctor获取的数组？

How can i properly declare an array of size that i get from a ctor?

EDIT：

发生的错误是：

incompatible types in assignment of ‘std::string* {aka std::basic_string<char>*}’ to ‘std::string* [0] 

而对于 int 数组：

incompatible types in assignment of ‘int*’ to ‘int [0]’

推荐答案

它们不是在C ++中声明静态数组的有效方式，数组大小需要在编译时知道。下面的代码不能在没有一些特殊扩展的标准C ++中编译。

They are not valid way of declaring static arrays in C++, array size needs to be known at compile time. Below code can't compile in standard C++ without some special extension.

std::string* A[];
int B[];
int C[];

如果你只是使用指针很好。 但是，最好考虑使用 std :: vector

If you are just playing with pointers that's fine. However, you'd better think of using std::vector

#include <vector>
std::vector<std::string> A;
std::vector<int> B;
std::vector<int> C;

我可以将您的代码重写为以下内容：

I may rewrite your code to below:

class MyQuickInitArray
{
public:
    MyQuickInitArray(int size)
      : A(size),
        B(size),
        C(size),
        size_(size),
        counter_(0)
    {     
    }

    std::string operator[](int j) const 
    {
        return A.at(j);
    }

private:
    std::vector<std::string> A;
    std::vector<int> B;
    std::vector<int> C;
    int size_;
    int counter_;
};

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