Two structs, one trait in Mojo

Unrelated types can satisfy the same trait, each in its own way.

trait Speaker:
    def speak(self) -> String:
        ...


@fieldwise_init
struct Dog(ImplicitlyCopyable, Movable, Speaker):
    var name: String

    def speak(self) -> String:
        return self.name + " says woof"


@fieldwise_init
struct Clock(ImplicitlyCopyable, Movable, Speaker):
    var hour: Int

    def speak(self) -> String:
        return "the time is " + String(self.hour)


def main():
    print(Dog("Rex").speak())
    print(Clock(9).speak())

How it works

1. Speaker requires only that a type can produce a String.
2. Dog builds its line from a name; Clock builds one from an hour.
3. Neither struct knows about the other, yet both answer speak().

Keywords and builtins used here

• Int
• Movable
• String
• def
• main
• print
• return
• self
• speak
• struct
• trait
• var

The run, in numbers

Lines

24

Characters to type

408

Tokens

103

Three-star pace

75 tpm

At the three-star pace of 75 tokens a minute, this run takes about 82 seconds.

Type this snippet

Step 2 of 5 in Traits, step 17 of 22 in Structs & traits.

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