如何使用 string(int, char) function 添加或更改声明字符串的值？

Question

I know there is a way to give a value of a specific character being repeated n times to a string while declaring it, like this:

string example(int, char);

But what if I didn't give it a value initially, is it possible to use the repeated character function later?

I tried doing this but it didn't work:

string example;
example(int, char);

I got this error "call of an object of a class type without appropriate operator() or conversion functions to pointer-to-function type"

Answer 1

You can't do exactly that, but here's the next best thing. If you need to increase/decrease size, you can use std::string::resize() , which has a second parameter to fill the new char s. So try this:

std::string foo;
foo.resize(10, 'A');
std::cout << foo << '\n';

And the output will be: AAAAAAAAAA

However, note that if you try this:

std::string a = "a";
a.resize(2, 'A');

a will become "aA" , because it does not overwrite the previous characters, only the new empty ones. To overwrite the previous ones, you can use std::fill :

std::string a = "aaa";
std::fill(a.begin(), a.end(), 'A');

And it'll become "AAA" .

[EDIT] As @churill said, reusing the constructor a = std::string(10, 'A') will also set the value of the string to "AAAAAAAAAA" , so you can use this as a simpler approach if you don't mind losing the previous value.