Rust book - Drop trait

• Drop trait allows to run arbitrary code when value goes out of scope

struct MyStruct {
	data: String
}

impl Drop for MyStruct {
	fn drop(&mut self) {
		println!("dropping MyStruct");
	}
}

fn main() {
	println!("before creating ms");
	let ms = MyStruct { data: String::from("hello world") };
	println!("after creating ms");
}

• The sequence of logs displayed is the following:

> before createing ms
> after createing ms
> dropping MyStruct 

• It is possible to drop values early using drop function from std::mem::drop, this can be useful when implementing locks, since the lock needs to be drop during the execution of the program, so another part of the program can get a hold of the lock.

struct MyStruct {
	data: String
}

impl Drop for MyStruct {
	fn drop(&mut self) {
		println!("dropping MyStruct");
	}
}

fn main() {
	println!("before creating ms");
	let ms = MyStruct { data: String::from("hello world") };
	println!("after creating ms");
}

• In this case the sequence of logs displayed is different, because ms goes out of scope early

> before createing ms
> dropping MyStruct 
> after createing ms