Objective-C iOS Development for Legacy & Enterprise Apps · レッスン

クラス、オブジェクト、メソッド

クラスの定義、オブジェクトの作成、インスタンスメソッドとクラスメソッドの実装を学び、振る舞いをカプセル化します。

「クラス、オブジェクト、メソッド」はCoddyKit上の無料Objective-C iOS Development for Legacy & Enterprise Appsレッスンです。これはレッスン1/4です。下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。これはObjective-C iOS Development for Legacy & Enterprise Apps学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Objective-C iOS Development for Legacy & Enterprise Appsコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

OOP Basics: Classes & Objects

Welcome to Object-Oriented Programming (OOP) in Objective-C! OOP helps organize code into reusable blueprints called classes.

From these blueprints, we create individual items called objects. Think of a class as a cookie cutter, and an object as a cookie!

Your First Class: Header File

Every Objective-C class has two main files: a .h (header) and a .m (implementation) file.

The header file (.h) declares what your class is and what it can do. It's like the public blueprint.

Here's how to declare a simple Person class:

// Person.h
#import <Foundation/Foundation.h>

@interface Person : NSObject

// Method declaration
- (void)sayHello;

@end

Class Implementation: Source File

The implementation file (.m) contains the actual code that makes your class work. It defines the behavior declared in the header.

Here, we implement the sayHello method for our Person class:

// Person.m
#import "Person.h"

@implementation Person

- (void)sayHello {
  NSLog(@"Hello from a Person object!");
}

@end

Bringing Classes to Life: Objects

Now that we have a Person class, let's create an object from it! Creating an object is also called instantiation.

In Objective-C, we use the alloc and init methods to create new objects. alloc reserves memory, and init initializes it.

Try running this example:

#import <Foundation/Foundation.h>

// Person.h (declared here for runnable example)
@interface Person : NSObject
- (void)sayHello;
@end

// Person.m (implemented here for runnable example)
@implementation Person
- (void)sayHello {
  NSLog(@"Hello from a Person object!");
}
@end

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    // Create a Person object
    Person *person1 = [[Person alloc] init];
    NSLog(@"Created a Person object: %@", person1);
  }
  return 0;
}

Instance Methods: Object Actions

Instance methods are actions that an individual object can perform. They usually work with data specific to that object.

To tell an object to perform an action, you send it a message. The syntax is [object methodName];.

Let's make our person1 object say hello:

#import <Foundation/Foundation.h>

@interface Person : NSObject
- (void)sayHello;
@end

@implementation Person
- (void)sayHello {
  NSLog(@"Hello from a Person object!");
}
@end

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    Person *person1 = [[Person alloc] init];
    [person1 sayHello]; // Sending the 'sayHello' message
  }
  return 0;
}

Methods with Arguments

Methods can also take arguments (or parameters) to customize their behavior. Objective-C uses a unique syntax for method arguments, making methods very descriptive.

The first argument is part of the method name, and subsequent arguments are labeled.

Let's add a method to our Person class that takes a name:

#import <Foundation/Foundation.h>

@interface Person : NSObject
- (void)sayHelloTo:(NSString *)name; // Method with one argument
@end

@implementation Person
- (void)sayHelloTo:(NSString *)name {
  NSLog(@"Hello, %@ from a Person object!", name);
}
@end

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    Person *person1 = [[Person alloc] init];
    [person1 sayHelloTo:@"Alice"]; // Sending message with argument
  }
  return 0;
}

Class Methods: Type Actions

Unlike instance methods, class methods (also known as static methods) belong to the class itself, not to a specific object.

They start with a + sign in their declaration and implementation. You call them directly on the class name, like [ClassName methodName];.

Class methods are often used for creating objects or utility functions related to the class.

#import <Foundation/Foundation.h>

@interface Person : NSObject
+ (void)aboutThisClass; // Class method declaration
@end

@implementation Person
+ (void)aboutThisClass {
  NSLog(@"This is the Person class, used to create person objects.");
}
@end

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    [Person aboutThisClass]; // Calling a class method
  }
  return 0;
}

Class vs. Instance: Key Difference

Here's a quick summary of the main differences:

Instance Methods (-): Operate on a specific object's data. You need an object instance to call them.
Class Methods (+): Operate on the class itself, not an instance. You call them directly on the class name. They don't have access to instance variables.

Choose the right type based on whether the action needs specific object data or general class-related functionality.

Sending Messages in Objective-C

In Objective-C, calling a method is formally called sending a message to an object (or class).

The syntax [receiver messageName:argument]; means we're sending the messageName: message to the receiver object (or class).

This message-sending mechanism is a core part of Objective-C's dynamic nature.

Quick Check: Classes & Methods

Test your knowledge of Objective-C OOP fundamentals.

Recap: Classes, Objects & Methods

Great job! In this lesson, you learned:

What classes are (blueprints) and objects are (instances).
How to declare a class in a .h file and implement it in a .m file.
How to create objects using alloc and init.
The difference between instance methods (-) and class methods (+).
How Objective-C uses message sending to invoke methods.

You're now ready to build more complex, organized Objective-C applications!

よくある質問

「クラス、オブジェクト、メソッド」レッスンは無料ですか？

はい。「クラス、オブジェクト、メソッド」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Objective-C iOS Development for Legacy & Enterprise Appsコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Objective-C iOS Development for Legacy & Enterprise Appsコースには全4レッスンが含まれています。

「クラス、オブジェクト、メソッド」で何を学びますか？

クラスの定義、オブジェクトの作成、インスタンスメソッドとクラスメソッドの実装を学び、振る舞いをカプセル化します。ブラウザで直接実行するハンズオンコードでObjective-C iOS Development for Legacy & Enterprise Appsを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Objective-C iOS Development for Legacy & Enterprise Appsを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのObjective-C iOS Development for Legacy & Enterprise Appsは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。これはレッスン1/4です。

「クラス、オブジェクト、メソッド」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このObjective-C iOS Development for Legacy & Enterprise Appsレッスンでコードを書いて実行できますか？

はい。すべてのObjective-C iOS Development for Legacy & Enterprise Appsレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

このコースのすべてのレッスン

← Objective-C iOS Development for Legacy & Enterprise Appsに戻る