#import <Foundation/Foundation.h>
 
@interface CustomURLProtocol : NSURLProtocol
 
@end

+ canInitWithRequest: 
//抽象方法，子類給出是否能相應(yīng)該請(qǐng)求。如果響應(yīng)YES，說(shuō)明自己的CustomURLProtocol實(shí)現(xiàn)該請(qǐng)求。
 
+ canonicalRequestForRequest:
//抽象方法，重寫該方法，可以對(duì)請(qǐng)求進(jìn)行修改，例如添加新的頭部信息，修改，修改url等，返回修改后的請(qǐng)求。
 
+ requestIsCacheEquivalent:toRequest:
//看都是緩存了
 
- startLoading:
//開始下載，需要在該方法中發(fā)起一個(gè)請(qǐng)求，對(duì)于NSURLConnection來(lái)說(shuō)，就是創(chuàng)建一個(gè)NSURLConnection，對(duì)于NSURLSession，就是發(fā)起一個(gè)NSURLSessionTask 。一般下載前需要設(shè)置該請(qǐng)求正在進(jìn)行下載，防止多次下載的情況發(fā)生
 
- stopLoading:
//停止相應(yīng)請(qǐng)求，清空請(qǐng)求Connection 或 Task

//導(dǎo)入自定義NSURLProtocol類
#import "CustomURLProtocol.h"
//在ViewDidLoad中添加攔截網(wǎng)絡(luò)請(qǐng)求的代碼
//注冊(cè)網(wǎng)絡(luò)請(qǐng)求攔截
[NSURLProtocol registerClass:[CustomURLProtocol class]];
//在ViewWillDisappear中添加取消網(wǎng)絡(luò)攔截的代碼
//取消注冊(cè)網(wǎng)絡(luò)請(qǐng)求攔截
[NSURLProtocol unregisterClass:[CustomURLProtocol class]];

//直接在AppDelegate中的didFinishLaunchingWithOptions注冊(cè)網(wǎng)絡(luò)攔截代碼
//注冊(cè)Protocol
[NSURLProtocol registerClass:[CustomURLProtocol class]];
NSURLProtocol使用實(shí)例

#define URLProtocolHandledKey @"URLProtocolHandledKey"
 
+ (BOOL)canInitWithRequest:(NSURLRequest *)request{
 //只處理http和https請(qǐng)求
  NSString *scheme = [[request URL] scheme];
  if ( ([scheme caseInsensitiveCompare:@"http"] == NSOrderedSame ||
   [scheme caseInsensitiveCompare:@"https"] == NSOrderedSame)){
    //看看是否已經(jīng)處理過(guò)了，防止無(wú)限循環(huán)
    if ([NSURLProtocol propertyForKey:URLProtocolHandledKey inRequest:request]) {
      return NO;
    }
    return YES;
  }
  return NO;
}
 
+ (NSURLRequest *) canonicalRequestForRequest:(NSURLRequest *)request {
   /** 可以在此處添加頭等信息 */
  NSMutableURLRequest *mutableReqeust = [request mutableCopy];
  mutableReqeust = [self redirectHostInRequset:mutableReqeust];
  return mutableReqeust;
}
 
+(NSMutableURLRequest*)redirectHostInRequset:(NSMutableURLRequest*)request{
  if ([request.URL host].length == 0) {
    return request;
  }
 
  NSString *originUrlString = [request.URL absoluteString];
  NSString *originHostString = [request.URL host];
  NSRange hostRange = [originUrlString rangeOfString:originHostString];
  if (hostRange.location == NSNotFound) {
    return request;
  }
  //定向薄荷喵到主頁(yè)
  NSString *ip = @"bohemiao.com";
 
  // 替換域名
  NSString *urlString = [originUrlString stringByReplacingCharactersInRange:hostRange withString:ip];
  NSURL *url = [NSURL URLWithString:urlString];
  request.URL = url;
 
  return request;
}
 
+ (BOOL)requestIsCacheEquivalent:(NSURLRequest *)a toRequest:(NSURLRequest *)b{
  return [super requestIsCacheEquivalent:a toRequest:b];
}
 
- (void)startLoading{
  NSMutableURLRequest *mutableReqeust = [[self request] mutableCopy];
  //標(biāo)示該request已經(jīng)處理過(guò)了，防止無(wú)限循環(huán)
  [NSURLProtocol setProperty:@YES forKey:URLProtocolHandledKey inRequest:mutableReqeust];
  self.connection = [NSURLConnection connectionWithRequest:mutableReqeust delegate:self];
  //使用NSURLSession也是一樣的
}
 
- (void)stopLoading{
  [self.connection cancel];
}
 
- (void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
  [self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
}
 
- (void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
  [self.client URLProtocol:self didLoadData:data];
}
 
- (void) connectionDidFinishLoading:(NSURLConnection *)connection {
  [self.client URLProtocolDidFinishLoading:self];
}
 
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
  [self.client URLProtocol:self didFailWithError:error];
}

@protocol NSURLProtocolClient <NSObject>
 
//請(qǐng)求重定向
- (void)URLProtocol:(NSURLProtocol *)protocol wasRedirectedToRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)redirectResponse;
 
// 響應(yīng)緩存是否合法
- (void)URLProtocol:(NSURLProtocol *)protocol cachedResponseIsValid:(NSCachedURLResponse *)cachedResponse;
 
//剛接收到Response信息
- (void)URLProtocol:(NSURLProtocol *)protocol didReceiveResponse:(NSURLResponse *)response cacheStoragePolicy:(NSURLCacheStoragePolicy)policy;
 
//數(shù)據(jù)加載成功
- (void)URLProtocol:(NSURLProtocol *)protocol didLoadData:(NSData *)data;
 
//數(shù)據(jù)完成加載
- (void)URLProtocolDidFinishLoading:(NSURLProtocol *)protocol;
 
//數(shù)據(jù)加載失敗
- (void)URLProtocol:(NSURLProtocol *)protocol didFailWithError:(NSError *)error;
 
//為指定的請(qǐng)求啟動(dòng)驗(yàn)證
- (void)URLProtocol:(NSURLProtocol *)protocol didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge;
 
//為指定的請(qǐng)求取消驗(yàn)證
- (void)URLProtocol:(NSURLProtocol *)protocol didCancelAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge;
 
@end