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v24.6

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Mojo trait

Copyable

The Copyable trait denotes a type whose value can be copied.

Example implementing the Copyable trait on Foo which requires the __copyinit__ method:

struct Foo(Copyable):
    var s: String

    @implicit
    fn __init__(out self, s: String):
        self.s = s

    fn __copyinit__(out self, other: Self):
        print("copying value")
        self.s = other.s
struct Foo(Copyable):
    var s: String

    @implicit
    fn __init__(out self, s: String):
        self.s = s

    fn __copyinit__(out self, other: Self):
        print("copying value")
        self.s = other.s

You can now copy objects inside a generic function:

fn copy_return[T: Copyable](foo: T) -> T:
    var copy = foo
    return copy

var foo = Foo("test")
var res = copy_return(foo)
fn copy_return[T: Copyable](foo: T) -> T:
    var copy = foo
    return copy

var foo = Foo("test")
var res = copy_return(foo)
copying value
copying value

Implemented traits​

AnyType, UnknownDestructibility

Methods​

__copyinit__​

__copyinit__(out self: _Self, existing: _Self, /)

Create a new instance of the value by copying an existing one.

Args:

  • ​existing (_Self): The value to copy.