int main(int argc, const char * argv[]) {
  @autoreleasepool {
    [[NSRunLoop currentRunLoop]run];
  }
  return 0;
}

#import <Foundation/Foundation.h>

@interface BNRLogger : NSObject<NSURLSessionDataDelegate>
@property(nonatomic) NSDate *lastTime;

-(NSString *) lastTimeString;
-(void)updateLastTime: (NSTimer *) t;

@end

#import "BNRLogger.h"

@implementation BNRLogger

-(NSString *)lastTimeString
{
  static NSDateFormatter *dateFormatter=nil;

  if(!dateFormatter)
  {
    dateFormatter =[[NSDateFormatter alloc]init];
    [dateFormatter setTimeStyle:NSDateFormatterMediumStyle];
    [dateFormatter setDateStyle:NSDateFormatterMediumStyle];

    NSLog(@"created dateFormatter");
  }
  return [dateFormatter stringFromDate:self.lastTime];
}

-(void)updateLastTime:(NSTimer *)t
{
  NSDate *now=[NSDate date];
  [self setLastTime:now];
  NSLog(@"Just set time to %@",self.lastTimeString);
}

@end

#import <Foundation/Foundation.h>
#import "BNRLogger.h"

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    BNRLogger *logger=[[BNRLogger alloc]init];

    __unused NSTimer *timer=[NSTimer scheduledTimerWithTimeInterval:2.0 target:logger selector:@selector(updateLastTime:) userInfo:nil repeats:YES];

    [[NSRunLoop currentRunLoop]run];
  }
  return 0;
}

#import <Foundation/Foundation.h>
#import "BNRLogger.h"

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    BNRLogger *logger=[[BNRLogger alloc]init];

    //URL是一張圖片的下載鏈接
    NSURL *url = [NSURL URLWithString:@"http://image.baidu.com/search/down?tn=download&ipn=dwnl&word=download&ie=utf8&fr=result&url=http%3A%2F%2Fimg.xiazaizhijia.com%2Fuploads%2F2016%2F0914%2F20160914112151862.jpg&thumburl=http%3A%2F%2Fimg4.imgtn.bdimg.com%2Fit%2Fu%3D2349180720%2C2436282788%26fm%3D11%26gp%3D0.jpg"];

    NSURLRequest *request = [NSURLRequest requestWithURL:url];

    __unused NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:logger delegateQueue:[NSOperationQueue mainQueue]];

    __unused NSTimer *timer=[NSTimer scheduledTimerWithTimeInterval:2.0 target:logger selector:@selector(updateLastTime:) userInfo:nil repeats:YES];

    //4.根據(jù)會(huì)話對(duì)象創(chuàng)建一個(gè)Task(發(fā)送請(qǐng)求）
    NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request];

    //5.執(zhí)行任務(wù)
    [dataTask resume];

    [[NSRunLoop currentRunLoop]run];

  }
  return 0;
}

#import <Foundation/Foundation.h>

@interface BNRLogger : NSObject<NSURLSessionDataDelegate>
@property (nonatomic, strong) NSMutableData *responseData;
@property(nonatomic) NSDate *lastTime;

-(NSString *) lastTimeString;
-(void)updateLastTime: (NSTimer *) t;

@end

#import "BNRLogger.h"

@implementation BNRLogger

-(NSMutableData *)responseData
{
  if (_responseData == nil) {
    _responseData = [NSMutableData data];
  }
  return _responseData;
}

-(NSString *)lastTimeString
{
  static NSDateFormatter *dateFormatter=nil;

  if(!dateFormatter)
  {
    dateFormatter =[[NSDateFormatter alloc]init];
    [dateFormatter setTimeStyle:NSDateFormatterMediumStyle];
    [dateFormatter setDateStyle:NSDateFormatterMediumStyle];

    NSLog(@"created dateFormatter");
  }
  return [dateFormatter stringFromDate:self.lastTime];
}

-(void)updateLastTime:(NSTimer *)t
{
  NSDate *now=[NSDate date];
  [self setLastTime:now];
  NSLog(@"Just set time to %@",self.lastTimeString);
}

//1.接收到服務(wù)器響應(yīng)的時(shí)候調(diào)用該方法
-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler
{
  //在該方法中可以得到響應(yīng)頭信息，即response
  NSLog(@"didReceiveResponse--%@",[NSThread currentThread]);
  NSLog(@"響應(yīng)");
  //注意：需要使用completionHandler回調(diào)告訴系統(tǒng)應(yīng)該如何處理服務(wù)器返回的數(shù)據(jù)
  //默認(rèn)是取消的
  /*
   NSURLSessionResponseCancel = 0,    默認(rèn)的處理方式，取消
   NSURLSessionResponseAllow = 1,     接收服務(wù)器返回的數(shù)據(jù)
   NSURLSessionResponseBecomeDownload = 2,變成一個(gè)下載請(qǐng)求
   NSURLSessionResponseBecomeStream    變成一個(gè)流
   */

  completionHandler(NSURLSessionResponseAllow);
}

//2.接收到服務(wù)器返回?cái)?shù)據(jù)的時(shí)候會(huì)調(diào)用該方法，如果數(shù)據(jù)較大那么該方法可能會(huì)調(diào)用多次
-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
{
  NSLog(@"didReceiveData--%@",[NSThread currentThread]);
  NSLog(@"返回");
  //拼接服務(wù)器返回的數(shù)據(jù)
  [self.responseData appendData:data];
}

//3.當(dāng)請(qǐng)求完成(成功|失敗)的時(shí)候會(huì)調(diào)用該方法，如果請(qǐng)求失敗，則error有值
-(void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
  NSLog(@"didCompleteWithError--%@",[NSThread currentThread]);
  NSLog(@"完成");
  if(error == nil)
  {
    //解析數(shù)據(jù)
    NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:self.responseData options:kNilOptions error:nil];
    NSLog(@"%@",dict);
  }
}

@end

 //在”輔助對(duì)象”方法應(yīng)用程序中的main.m中加入這行代碼
 [[NSNotificationCenter defaultCenter]addObserver:logger selector:@selector(zoneChange:) name:NSSystemTimeZoneDidChangeNotification object:nil];

 //在”輔助對(duì)象”方法應(yīng)用程序中的BNRLogger.m中加入這行代碼
 -(void)zoneChange:(NSNotification *)note
{
  NSLog(@"The system time zone has changed!");
}

[[NSNotificationCenter defaultCenter]addObserver:logger selector:@selector(zoneChange:) name:NSSystemTimeZoneDidChangeNotification object:nil];

[[NSNotificationCenter defaultCenter]addObserverForName:NSSystemTimeZoneDidChangeNotification object:nil queue:[NSOperationQueue mainQueue] usingBlock:^(NSNotification *note){
      NSLog(@"The system time zone has changed!");
    }];

-(void)zoneChange:(NSNotification *)note
{
  NSLog(@"The system time zone has changed!");
}