@fieldwise_init

You can add the @fieldwise_init decorator on a struct to generate the field-wise __init__() constructor.

For example, consider a simple struct like this:

@fieldwise_init
struct MyPet:
    var name: String
    var age: Int
@fieldwise_init
struct MyPet:
    var name: String
    var age: Int

Mojo sees the @fieldwise_init decorator and synthesizes a fieldwise constructor, the result being as if you had actually written this:

struct MyPet:
    var name: String
    var age: Int

    fn __init__(out self, owned name: String, age: Int):
        self.name = name^
        self.age = age
struct MyPet:
    var name: String
    var age: Int

    fn __init__(out self, owned name: String, age: Int):
        self.name = name^
        self.age = age

This decorator replaces one function of the @value decorator. To synthesize the copy constructor and move constructor, add the Copyable and Movable traits to your struct.

For more information about these lifecycle methods, read Life of a value.