Rust: Function on Types (impl)

Status: Courses

1. Types like struct and enums can have functions & methods attached to them using impl.

   // define struct 
   struct Player {
   	name: String,
   	iq: u8,
   	friends: u8,
   	score: u16
   }
   // define impl 
   impl Player {
   	// Initialize with Name
   	fn with_name(name: &str) -> Player {
   		Player {
   			name: name.to_string(),
   			iq: 100, 
   			friends: 100,
   			score: 100
   		}
   	}
     // Get friends field
   	fn get_friends(&self) -> u8 {
   		self.friends
   	}
   }
   
   fn main() {
   	// Init with name
   	let player1 = Player::with_name("Joe");
   	// Get the friends field
   	let player1_friends = player1.get_friends();
   	// Get the friends field another way. 
   	let player1_friend2 = Player::get_friends(&player);
   }

2. In impl block, there can be 2 types of functions

   1. With self type as the first parameter - Instance Methods
      1. The Instance Method can only be called on the existing variable of type. For ex: ****the ****get_friends function in the above code.
      2. Instance Methods also have 3 variants
         1. self as the first parameter - Calling this method will consume the type, you cannot use the type anymore.
         2. &self as the first parameter - Provides read-only access to self
         3. &mut self as the first parameter - Provides mutable access to self
   2. Without self type as the first parameter - Associated Methods
      1. Associated Methods don't require existing variables of the type. For ex: ****the ****with_name function in the above code.