# Methods and Associated Functions

Methods are similar to functions in that we declare them with the `fn` keyword and they have parameters and return a value. However, unlike functions, Methods are defined within the context of a struct (or enum), and either refers to that type or mutates it. The first parameter of a method is always `self`, which represents the instance of the struct the method is being called on.

Associated functions are very similar to methods, in that they are also defined in the context of a struct or enum, but they do not actually use any of the data in the struct and as a result do not take self as a parameter. Associated functions could be standalone functions, but they are included in a specific type for organizational or semantic reasons.

To declare methods and associated functions for a struct or enum, use an impl block. Here, `impl` stands for implementation.

``````script;

struct Foo {
bar: u64,
baz: bool,
}

impl Foo {
// this is a _method_, as it takes `self` as a parameter.
fn is_baz_true(self) -> bool {
self.baz
}

// this is an _associated function_, since it does not take `self` as a parameter.
fn new_foo(number: u64, boolean: bool) -> Foo {
Foo {
bar: number,
baz: boolean,
}
}
}

fn main() {
let foo = Foo::new_foo(42, true);
assert(foo.is_baz_true());
}
``````

To call a method, simply use dot syntax: `foo.iz_baz_true()`.

Similarly to free functions, methods and associated functions may accept `ref mut` parameters. For example:

``````struct Coordinates {
x: u64,
y: u64,
}

impl Coordinates {
fn move_right(ref mut self, distance: u64) {
self.x += distance;
}
}
``````

and when called:

``````    let mut point = Coordinates { x: 1, y: 1 };
point.move_right(5);
assert(point.x == 6);
assert(point.y == 1);
``````