3個Block替換Delegate的場景

 Delegate定義

#import <Foundation/Foundation.h>

@class ZYNetworkFetcher;

@protocol ZYNetworkFetcherDelegate <NSObject>
-(void)networkFetcher:(ZYNetworkFetcher *)networkfetcher didfinishWithData:(NSData *)data;
@end

@interface ZYNetworkFetcher : NSObject

@property (nonatomic,weak) id< ZYNetworkFetcherDelegate> delegate;
-(instance)initWithURL:(NSURL *)url;
-(void)start;

@end

 

Block定義

#import <Foundation/Foundation.h>

typedef void(^ZYNetworkFetcherCompletionHandle01)(NSData *data);
typedef void(^ZYNetworkFetcherCompletionHandle02)(NSData *data, NSError *error);

@interface ZYNetworkFetcher : NSObject

-(instance)initWithURL:(NSURL *)url;
-(void)startWithCompletionHandle1:(ZYNetworkFetcherCompletionHandle01)handle;
-(void)startWithCompletionHandle2:(ZYNetworkFetcherCompletionHandle02)handle;

@end

 

 

場景一

在一個UIViewController中，存在2個UITable，那麼在protocol的方法實現中，須要經過if/else區分是哪個table，代碼就被拉得很長，若是用block替代方案，某個table直接在API方法中傳入對應的block便可。 

好處：使用block塊調用更方便，代碼更清晰且API更緊緻，block中還能捕獲變量，

-(void)startMain
{
    NSURL *url01 = [[NSURL alloc] initWithString:@"https://www.baidu.com"];
    _obj01 = [[ZYNetworkFetcher alloc] initWithURL:url01];
    _obj01.delegate = self;
    [_obj01 start];
    
    NSURL *url02 = [[NSURL alloc] initWithString:@"https://www.google.com"];
    _obj02 = [[ZYNetworkFetcher alloc] initWithURL:url02];
    _obj02.delegate = self;
    [_obj02 start];
}


-(void)networkFetcher:(ZYNetworkFetcher *)networkfetcher didfinishWithData:(NSData *)data
{
    // 須要判斷是哪個對象的回調 
    if (networkfetcher == _obj01) { _objData01 = data; } else if(networkfetcher == _obj02){ _objData02 = data; }
}

-(void)startMain
{
    NSURL *url01 = [[NSURL alloc] initWithString:@"https://www.baidu.com"];
    _obj01 = [[ZYNetworkFetcher alloc] initWithURL:url01];
    [_obj01 startWithCompletionHandle1:^(NSData *data){
        _objData01 = data;
    }];
    
    NSURL *url02 = [[NSURL alloc] initWithString:@"https://www.google.com"];
    _obj02 = [[ZYNetworkFetcher alloc] initWithURL:url02];
    [_obj02 startWithCompletionHandle1:^(NSData *data){
        _objData02 = data;
    }];
}

 

 

場景二

網絡請求響應有成功和失敗兩種結果，一個block就能完成對成功和失敗結果的處理。

 

有考慮用2個block分別處理，但這樣不是最優。好比在處理響應成功的過程當中發現錯誤，就得用失敗的block處理，這時就會有重複性代碼。

-(void)startMain
{
    NSURL *url01 = [[NSURL alloc] initWithString:@"https://www.baidu.com"];
    _obj01 = [[ZYNetworkFetcher alloc] initWithURL:url01];
    [_obj01 startWithCompletionHandle2:^(NSData *data, NSError *error){
        if (error) {
            // ......
        } else {
            // ......
        }
    }];
    
    NSURL *url02 = [[NSURL alloc] initWithString:@"https://www.google.com"];
    _obj02 = [[ZYNetworkFetcher alloc] initWithURL:url02];
    [_obj02 startWithCompletionHandle2:^(NSData *data, NSError *error){
        if (error) {
            // ......
        } else {
            // ......
        }
    }];
}

 

場景三

在API中，添加queue參數，能夠將block回調任務提交到指定的queue。

 

好處：方便調用者對block的調度