Interfaces

Interfaces describe behavior. Any value with the required methods can satisfy an interface.

Inline Interfaces

Use iface to describe the methods a value must provide:

fn sayHi(sayer: iface {
    say(msg: string) void
}) void {
    sayer.say("Hi")
}

Structs Implementing Interfaces

Define a struct and add methods with impl:

struct SayStruct {}

impl SayStruct {
    fn say(msg: string) void {
        println(msg)
    }
}

sayHi(SayStruct())

Named Interfaces

Use type to name an interface:

type helloer: iface {
    sayHello() void
}

Named interfaces make function signatures easier to read:

fn interfaceTest(obj: helloer) void {
    obj.sayHello()
}

Example

type helloer: iface {
    sayHello() void
}

struct User {
    name: string
}

impl User {
    fn init(self: User, name: string) void {
        self.name = name
    }

    fn sayHello(self: User) void {
        println(`Hi! I am ${self.name}!`)
    }
}

const john = User("John")
interfaceTest(john)