This has been a large topic, but we have two more aspects to consider for traits: inheritance and deriving. One that should be familiar if you're used to any form of object-oriented programming.
This is very similar to inheritance within C++ and C#:
trait One
{
fn one(&self);
}
trait OneTwo : One
{
fn onetwo(&self);
}The code that implements OneTwo must also implement One (the same as when we overrode the default method, we still had to define is_done), therefore:
struct Three;
impl One for Three
{
fn one(&self)
{
println!("one");
}
}
impl OneTwo for Three
{
fn onetwo(&self)
{
println!("onetwo");
}
}And the result is as follows:
If we omitted the impl One block, we would get a compilation error complaining that impl OneTwo requires impl One to exist.