如何优雅地初始化vector< char *>与字符串文字？ [英] How to elegantly initialize vector<char *> with string literal?

问题描述

问题来自C ++ Primer 5th Edition上的练习：

The problem comes from an exercise on C++ Primer 5th Edition:

编写一个程序以从char列表中分配元素*指向C样式字符串的指针
指向字符串向量。

Write a program to assign the elements from a list of char* pointers to C-style character strings to a vector of strings.

---------- ------原始问题----------

----------------Oringinal Question------------

首先，我尝试以下一些直接方法：

First I try the following somewhat direct way:

vector<char *> vec = {"Hello", "World"};
vec[0][0] = 'h';

但是在编译代码时我得到了警告：

But compiling the code I get a warning:

temp.cpp:11:43: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings]
     vector<char *> vec = {"Hello", "World"};
                                           ^ 

运行./a.out我得到

And running the ./a.out I get a

Segmentation fault (core dumped)

我认为这是因为我尝试写入const char。所以我尝试另一种方式：

I think it is because I try to write to a const char. So I try another way:

char s1[] = "Hello", s2[] = "World";
vector<char *> vec = {s1, s2};
vec[0][0] = 'h';

这次可以。但这似乎有些乏味。

It is OK this time. But it seems a little tedious. Is there any other elegant way to initialize a vector with string literal?

推荐答案

这里是一种方法：

template <size_t N>
void append_literal(std::vector<char*>& v, const char (&str)[N]) {
    char* p = new char[N];
    memcpy(p, str, N);
    v.push_back(p);
}

std::vector<char*> v;
append_literal(v, "Hello");
append_literal(v, "World");

只需记住：

void clear(std::vector<char*>& v) {
    for (auto p : v) delete[] p;
}

尽管从问题的措辞来看，如果无论如何，它都是 vector< const char *> ，就好像它是 vector< char *> （您复制时不会修改源，所以可以修改源也没关系），因此我会坚持练习，就像您刚做过一样：

Although from the wording of the question, syntactically it's the same work either way if it was a vector<const char*> as if it were a vector<char*> anyway (you're not modifying the source when you're copy, so doesn't matter if you could modify the source), so I would stick to the exercise as if you just did:

std::vector<const char*> v{"Hello", "World!"};

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