Trait copy_from_str::CopyFromStrExt[−]

pub trait CopyFromStrExt {
    fn copy_from_str(&mut self, src: &str);
}

Extension method for copying a string into another string.

Required Methods

Copies all elements from src into self, using a memcpy.

The length of src must be the same as self.

Panics

This function will panic if the two strings have different lengths.

Examples

Copying two elements from a string into another:

use copy_from_str::CopyFromStrExt;

let src = "abcd";
let mut dst = String::from("  ");

dst.copy_from_str(&src[2..]);

assert_eq!(src, "abcd");
assert_eq!(dst, "cd");

Rust enforces that there can only be one mutable reference with no immutable references to a particular piece of data in a particular scope. Because of this, attempting to use copy_from_str on a single string will result in a compile failure:

ⓘThis example deliberately fails to compile
use copy_from_str::CopyFromStrExt;

let mut string = String::from("abcde");

string[..2].copy_from_str(&string[3..]); // compile fail!

To work around this, we can use split_at_mut to create two distinct sub-strings from a string:

use copy_from_str::CopyFromStrExt;

let mut string = String::from("abcde");

{
    let (left, right) = string.split_at_mut(2);
    left.copy_from_str(&right[1..]);
}

assert_eq!(string, "decde");

Implementors