Mojo trait

Sized

The Sized trait describes a type that has an integer length (such as a string or array).

Any type that conforms to Sized or SizedRaising works with the built-in len() function.

The Sized trait requires a type to implement the __len__() method. For example:

struct Foo(Sized):
    var length: Int

    fn __len__(self) -> Int:
        return self.length

You can pass an instance of Foo to the len() function to get its length:

var foo = Foo(42)
print(len(foo) == 42)

True

Note: If the __len__() method can raise an error, use the SizedRaising trait instead.

Implemented traits

alias __del__is_trivial

A flag (often compiler generated) to indicate whether the implementation of __del__ is trivial.

The implementation of __del__ is considered to be trivial if:

The struct has a compiler-generated trivial destructor and all its fields have a trivial __del__ method.

In practice, it means that the __del__ can be considered as no-op.

__len__(self: _Self) -> Int

Get the length of the type.

Returns:

Int: The length of the type.