Rust Auto-dereferencing Simple Deref example
Example
Deref has a simple rule: if you have a type T and it implements Deref<Target=F>, then &T coerces to &F, compiler will repeat this as many times as needed to get F, for example:
fn f(x: &str) -> &str { x }
fn main() {
// Compiler will coerce &&&&&&&str to &str and then pass it to our function
f(&&&&&&&"It's a string");
}
Deref coercion is especially useful when working with pointer types, like Box or Arc, for example:
fn main() {
let val = Box::new(vec![1,2,3]);
// Now, thanks to Deref, we still
// can use our vector method as if there wasn't any Box
val.iter().fold(0, |acc, &x| acc + x ); // 6
// We pass our Box to the function that takes Vec,
// Box<Vec> coerces to Vec
f(&val)
}
fn f(x: &Vec<i32>) {
println!("{:?}", x) // [1,2,3]
}
