自作クラスに簡単にdelegateを設定する

XCodeでアプリを作成していると，delegateメソッドを結構使います．

自分で作成したクラスでもdelegateが使えたら便利なのに…と思う事はあると思います．

そこで，簡単にdelegateを実装する手順を示します．

今回はMyDelegateSampleと言うクラスを作成し，ViewControllerから呼び出してdelegateを受け取ると言う想定です．

ソース中にコメントを埋め込んでいますので，解説は特に書きません．

MyDelegateSample.h

#import <Foundation/Foundation.h>

// Define Delegate
@protocol MyDelegateSampleDelegate <NSObject>

// Declare Delegate methods.
// Only declaration. Implements shoud be done by ViewController
- (void)sampleDelegate;
- (void)sampleDelegateWithParameter:(NSInteger)val;

@end

@interface MyDelegateSample : NSObject

// Define property so that it could be seen from user object
@property (nonatomic, assign) id<MyDelegateSampleDelegate> delegate;

// initializer
- (id)init;

// Method which calls delegate
- (void)fireDelegate;
- (void)fireDelegateWithParameter;

@end

MyDelegateSample.m

#import "MyDelegateSample.h"

@implementation MyDelegateSample

// Initializer Implement
- (id)init
{
    if (self = [super init]) {
        // Do initilaization if needed
    }
    return self;
}

// Fire delegates
- (void)fireDelegate
{
    // check if user has implemeted the delegate method
    if ([self.delegate respondsToSelector:@selector(sampleDelegate)])
    {
        // fire sampleDelegate
        [_delegate sampleDelegate];
    }
}

- (void)fireDelegateWithParameter
{
    // check if user has implemeted the delegate method
    if ([self.delegate respondsToSelector:@selector(sampleDelegateWithParameter:)])
    {
        // fire sampleDelegate
        [_delegate sampleDelegateWithParameter:10];
    }
}
@end

ViewController.h

#import <UIKit/UIKit.h>
#import "MyDelegateSample.h"


@interface ViewController : UIViewController<MyDelegateSampleDelegate>

@end

ViewController.m

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
    
    // Create MyDelagateSample Instance
    MyDelegateSample* myDelegate = [[MyDelegateSample alloc]init];
    
    // Set myDelegate's delegate to self
    myDelegate.delegate = self;
    
    // Fire first sampleDelegate
    [myDelegate fireDelegate];
    
    // Fire second sampleDelegateWithParameter
    [myDelegate fireDelegateWithParameter];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

// Implemets Delegate Methods
- (void)sampleDelegate
{
    NSLog(@"sampleDelegate is fired");
}

- (void)sampleDelegateWithParameter:(NSInteger)val
{
    NSLog(@"sampleDelegateWithParameter is fired with value %ld", (long)val);
}

@end

Single View Applicationを作成して，上記のコードを書いてシミュレーターで実行すると，NSLogが二回出力されるのが確認できます．

実際のdelegateメソッドの中では色々と処理を別スレッドでしますので，ViewControllerでdelegateメソッドがいつ呼ばれるかは判りません．