带字符串追加的旧锈代码每晚中断

Question

I have a line in some of my older rust code that uses append() , I checked the recent docs and append seem's to have been removed from std::string::String . my line of code is:

hex_to_bin(x).to_string().append(hex_to_bin(y))

main.rs:34:29: 34:50 error: type `collections::string::String` does not implement any method in scope named `append`
main.rs:34   hex_to_bin(x).to_string().append(hex_to_bin(y))

so according to the docs I thought push_str() would be the same, but when switched I get

main.rs:34:3: 34:52 error: mismatched types: expected `collections::string::String`, found `()` (expected struct collections::string::String, found ())
main.rs:34   hex_to_bin(x).to_string().push_str(hex_to_bin(y))

how can I convert this line of code correctly?

Answer 1

push_str is declared as:

fn push_str(&mut self, string: &str)

This means it operates on a mutable String, and returns () . Without seeing the rest of your code, my guess is that you're trying to pass the result of push_str to something that is expecting a String - perhaps you're expecting to assign the result to a String? Instead you would want to maintain a mutable String and call push_str to append the hex_to_bin(y) to it.