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iteratorrust

Iterating over a slice's values instead of references in Rust?


When looping over a slice of structs, the value I get is a reference (which is fine), however in some cases it's annoying to have to write var as (*var) in many places.

Is there a better way to avoid re-declaring the variable?

fn my_fn(slice: &[MyStruct]) {
    for var in slice {
        let var = *var;  // <-- how to avoid this?

        // Without the line above, errors in comments occur:

        other_fn(var);  // <-- expected struct `MyStruct`, found reference

        if var != var.other {
            // ^^ trait `&MyStruct: std::cmp::PartialEq<MyStruct>>` not satisfied
            foo();
        }
    }
}

Solution

  • You can remove the reference by destructuring in the pattern (old link):

    //  |
    //  v
    for &var in slice {
        other_fn(var);
    }
    

    However, this only works for Copy-types! If you have a type that doesn't implement Copy but does implement Clone, you could use the cloned() iterator adapter; see Chris Emerson's answer for more information.