Looking this example code
trait Animal {
fn make_sound(&self);
}
struct Dog;
impl Animal for Dog {
fn make_sound(&self) {
println!("Woof!");
}
}
struct Cat;
impl Animal for Cat {
fn make_sound(&self) {
println!("Meow!");
}
}
fn main() {
let dog = Dog;
let cat = Cat;
dog.make_sound();
cat.make_sound();
}
The function(method) make_sound() is just print a string.
I check the content of this function, make_sound() does not seems to invoke any information of Cat struct.
So I tried to remove &self parameter, but could not get the pass compiler.
Is &self necessary in the function of trait? Why?
Or where is my understanding wrong?
trait Animal {
fn make_sound();
}
struct Dog;
impl Animal for Dog {
fn make_sound() {
println!("Woof!");
}
}
struct Cat;
impl Animal for Cat {
fn make_sound() {
println!("Meow!");
}
}
fn main() {
let dog = Dog;
let cat = Cat;
dog.make_sound();
cat.make_sound();
}
No, a self parameter is not required for trait functions. However, if there is no self parameter, you can't use the obj.func() syntax since there is no instance to be provided. You have to do Type::func():
trait Animal {
fn make_sound();
}
struct Dog;
impl Animal for Dog {
fn make_sound() {
println!("Woof!");
}
}
struct Cat;
impl Animal for Cat {
fn make_sound() {
println!("Meow!");
}
}
fn main() {
Dog::make_sound();
Cat::make_sound();
}
Woof!
Meow!
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