Mojo Academy · 강의

필드와 init 메서드

struct의 상태를 초기화합니다.

필드와 __init__ 메서드은(는) CoddyKit의 무료 Mojo Academy 강의입니다. 이것은 4개 중 2번째 강의입니다. 아래에서 전체 강의를 무료로 읽을 수 있으며, 내장 코드 에디터와 24/7 AI 튜터와 함께 브라우저에서 직접 실습할 수 있습니다. 이 강의는 Mojo Academy 학습 경로의 일부이며, 진행 상황이 웹과 CoddyKit 앱에 동기화됩니다. Mojo Academy 강의에는 총 4개의 강의가 포함되어 있습니다.

이 강의의 일부는 아직 번역되지 않았으며 영어로 표시됩니다.

Fields Start Empty

Declaring fields gives a struct its shape, but it does not fill them in. You still need to set each field's starting value. 🧱

Meet init

The special method __init__ runs when you create an instance. Its job is to set up the struct's fields with real values.

fn __init__(out self):
    self.x = 0
    self.y = 0

The self Parameter

Inside __init__, self refers to the new instance being built. You assign to self.field to give that instance its data.

self.x = 0

Why out self

Writing out self tells Mojo this method is constructing the value, so self starts uninitialized and you must fill every field.

fn __init__(out self):

Taking Arguments

An initializer usually takes arguments so each instance can start with different data passed in by the caller.

fn __init__(out self, x: Int, y: Int):
    self.x = x
    self.y = y

Set Every Field

You must assign every field in __init__. Mojo will not let a struct exist with some fields left uninitialized.

Creating an Instance

To build a value, call the struct like a function. Mojo runs __init__ and hands you back a ready instance.

var p = Point(3, 4)

Reading a Field

Once built, reach a field with dot access. So p.x reads the x you stored when the instance was created.

print(p.x, p.y)

Arguments Map to Fields

A common pattern is naming arguments like the fields and assigning each across. This keeps the initializer easy to read.

self.x = x
self.y = y

Default Starting Values

You can give fields sensible defaults by assigning constants in __init__ when no useful argument is provided by the caller.

fn __init__(out self):
    self.x = 0
    self.y = 0

The Full Picture

Fields declare what data exists; __init__ decides its starting value. Together they turn a blueprint into a usable instance.

struct Point:
    var x: Int
    var y: Int
    fn __init__(out self, x: Int, y: Int):
        self.x = x
        self.y = y

Quick Check

Let us confirm how initialization works.

Recap

You used __init__ to set up fields when an instance is born. Next you will add methods so your type can act, not just hold data. ✨

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