Block学习一门:基本使用，使用block包NSURLRequest异步请求

首先，看一下下面的代码：

void (^myFirstBlock)(int theOne,int theTwo) = ^(int theOne,int theTwo){
        NSLog(@"====%d",theOne+theTwo);
    };
    myFirstBlock(100,300);

void:指的时返回数据类型，myFirstBlock：指的是block的名称，后面两个是參数。

等号右边的block的实现。

个人理解：block本身就是一个类。他的实例化就是一个对象。以下看看这个数据请求的封装，来好好理解这句话。

我把数据请求这一款，封装在了：WebService这个类中，先看h文件：

<span style="font-size:14px;">//
//  WebService.h
//  BlockDemo
//
//  Created by junyuan ji on 14-6-3.
//  Copyright (c) 2014年 junyuan ji. All rights reserved.
//

#import <Foundation/Foundation.h>

typedef void (^successBlock)(NSMutableURLRequest * request,NSMutableData * reciveData);
typedef  void (^errorBlock)(NSMutableURLRequest * request);
typedef void (^startBlock)(NSMutableURLRequest * request);
typedef void (^complectionBlock)(NSMutableURLRequest * request,NSMutableData * reciveData);

@interface WebService : NSObject<NSURLConnectionDataDelegate,NSURLConnectionDelegate>
{
   __block NSHTTPURLResponse * httpResponse;
}
@property (nonatomic,copy) successBlock successblock;
@property (nonatomic,copy) errorBlock errorblock;
@property (nonatomic,copy) startBlock startblock;
@property (nonatomic,copy) complectionBlock complectionblock;
@property (nonatomic,retain) __block NSMutableData * reciveMutableData;

-(void)StartUrl:(NSString *)path;

-(void)Url:(NSString *)path onSuccess:(successBlock)successBlock onError:(errorBlock)errorBlock onStart:(startBlock)startBlock onCompletion:(complectionBlock)complectionBlock;
@end</span><span style="font-size:18px;">
</span>

上面typedef是声明block，以下把block声明称属性。比方successblock是一个对象，自然能够把它声明成属性。

以下看看m文件的代码：

//
//  WebService.m
//  BlockDemo
//
//  Created by junyuan ji on 14-6-3.
//  Copyright (c) 2014年 junyuan ji. All rights reserved.
//

#import "WebService.h"

@implementation WebService

-(void)Url:(NSString *)path onSuccess:(successBlock)successBlock onError:(errorBlock)errorBlock onStart:(startBlock)startBlock onCompletion:(complectionBlock)complectionBlock
{
    [self StartUrl:path];
    self.successblock = ^(NSMutableURLRequest * request,NSMutableData * reciveData){
        if (httpResponse.statusCode == 200)
        {
           successBlock(request,reciveData);
        }
    };
    self.startblock = ^(NSMutableURLRequest *request){
        startBlock(request);
    };
    self.errorblock = ^(NSMutableURLRequest * request){
        errorBlock(request);
    };
    self.complectionblock = ^(NSMutableURLRequest * request,NSMutableData * reciveData){
        complectionBlock(request,reciveData);
    };
}
-(void)StartUrl:(NSString *)path
{
    NSURL * url = [NSURL URLWithString:path];
    NSMutableURLRequest * request1 = [NSMutableURLRequest requestWithURL:url];
    [NSURLConnection connectionWithRequest:request1 delegate:self];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
     NSLog(@"%s",__FUNCTION__);
    self.errorblock((NSMutableURLRequest *)connection.currentRequest);
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSLog(@"%s",__FUNCTION__);
    httpResponse = (NSHTTPURLResponse *)response;
    self.reciveMutableData = [NSMutableData dataWithCapacity:0];
    self.startblock((NSMutableURLRequest *)connection.currentRequest);
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
     NSLog(@"%s",__FUNCTION__);
    [self.reciveMutableData appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
     NSLog(@"%s",__FUNCTION__);
    self.complectionblock((NSMutableURLRequest *)connection.currentRequest,self.reciveMutableData);
}
@end

上面这几段代码，应该好好去理解，假设上面这段代码看懂了，block基本上也就掌握了。

以下看看怎样使用封装的这个类：

#import "AppDelegate.h"
#import "WebService.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];

    void (^myFirstBlock)(int theOne,int theTwo) = ^(int theOne,int theTwo){
        NSLog(@"====%d",theOne+theTwo);
    };
    myFirstBlock(100,300);

    [[[WebService alloc] init] Url:@"http://zhangmenshiting.baidu.com/data2/music/65532488/1490719597200128.mp3?xcode=f1ea4f162f276d435fc963a294370657c9d1e761819ce1d5" onSuccess:^(NSMutableURLRequest *request, NSMutableData *reciveData) {
        NSLog(@"reciveData = %@",reciveData);
    } onError:^(NSMutableURLRequest *request) {
        NSLog(@"error = ");
    } onStart:^(NSMutableURLRequest *request) {
        NSLog(@"start");
    } onCompletion:^(NSMutableURLRequest *request, NSMutableData *reciveData) {
        NSLog(@"completion");
    }];

    return YES;
}