string :: at和string :: operator []有什么区别？ [英] What is the difference between string::at and string::operator[]?

问题描述

在学校里，我曾教过 string :: at ，但是通过探索字符串库，我看到了 string :: operator [] ，这是我以前从未见过的。

I was taught string::at in school, but by exploring the string library I saw string::operator[], which I was never shown before.

我现在正在使用 operator [] 并没有t以来一直在使用，但是有什么区别？
这是一些示例代码：

I'm now using operator[] and haven't used at since, but what is the difference? Here is some sample code:

std::string foo = "my redundant string has some text";
std::cout << foo[5];
std::cout << foo.at(5);

在输出方面，它们基本相同，但是有一些我不知道的细微差别

They are essentially the same in terms of output, but are there some subtle differences I'm not aware of?

推荐答案

是的，有一个主要区别：使用 .at（） 对通过的索引进行范围检查，如果索引在 operator []的字符串末尾 在这种情况下只会带来未定义的行为。

Yes, there is one major difference: using .at() does a range check on index passed and throws an exception if it's over the end of the string while operator[] just brings undefined behavior in that situation.

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