PRHTTPURLProtocol.h文件

#import <Foundation/Foundation.h>

//繼承自NSURLProtocol
@interface PRHTTPURLProtocol : NSURLProtocol

@end

PRHTTPURLProtocol.m文件

#import "PRHTTPURLProtocol.h"
#import "PRCachedURLResponse.h"

//自定義唯一標示符
static NSString *const PRHTTPURLProtocolHandledKey = @"PRHTTPURLProtocolHandledKey"; 

@interface PRHTTPURLProtocol ()

@property (nonatomic, strong) NSURLConnection *connection;//網絡連接對象
@property (nonatomic, strong) NSMutableData *data;//網絡請求返回數據
@property (nonatomic, strong) NSURLResponse *response;//網絡返回封裝對象(包含推盛，數據峦阁，格式，請求鏈接等等)

@end

@implementation PRHTTPURLProtocol

//說白了這個函數是用來過濾網絡請求的協議的小槐，即滿足我設置的協議就給你返回yes拇派，允許你進行網絡通信荷辕，一旦返回no后續(xù)的網絡請求將不會被繼續(xù)執(zhí)行
+ (BOOL)canInitWithRequest:(NSURLRequest *)request
{
    //如果是非http https就不讓他通過
    if (![request.URL.scheme isEqualToString:@"http"] && ![request.URL.scheme isEqualToString:@"https"]) {
        return NO;
    }
    
    //看看是否已經處理過了凿跳，防止無限循環(huán)件豌，如果已經處理過(即設置了允許通過，就不再初始化了)
    if ([NSURLProtocol propertyForKey:PRHTTPURLProtocolHandledKey inRequest:request]) {
        return NO;
    }
    
    return YES;
}

+ (NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request
{
    return request;
}

- (void)startLoading
{
    //如果有緩存控嗜，就直接返回緩存的結果
    NSString *cacheKey = self.request.URL.absoluteString;
    PRCachedURLResponse *cachedResponse = [[CWObjectCache sharedCache] objectForKey:cacheKey];
    if (cachedResponse && cachedResponse.response && cachedResponse.data) {
        NSURLResponse *response = cachedResponse.response;
        NSData *data = cachedResponse.data;
        
        [self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
        [self.client URLProtocol:self didLoadData:data];
        [self.client URLProtocolDidFinishLoading:self];
        return;
    }
    
   //沒有緩存 返回這個新的請求
    NSMutableURLRequest *newRequest = [self.request mutableCopy];
    [newRequest setTimeoutInterval:15];
    //打標簽茧彤，防止無限循環(huán)
    [NSURLProtocol setProperty:@YES forKey:PRHTTPURLProtocolHandledKey inRequest:newRequest];
    self.connection = [NSURLConnection connectionWithRequest:newRequest delegate:self];
}

- (void)stopLoading
{
    [self.connection cancel];
}

#pragma mark - NSURLConnection delegate

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [[self client] URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
    
    // cache image only
    NSString *MIMEType = [response.MIMEType lowercaseString];
    if (![MIMEType hasPrefix:@"image"]) {
        return;
    }
    
    //保存網絡獲取的數據和數據對象
    self.data = [[NSMutableData alloc] init];
    self.response = response;
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [[self client] URLProtocol:self didLoadData:data];
    
    //累加數據
    [self.data appendData:data];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    [[self client] URLProtocol:self didFailWithError:error];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    [[self client] URLProtocolDidFinishLoading:self];
    
    if (!self.response || [self.data length] == 0) {
        return;
    }
        
    //緩存對應url的數據和數據對象(序列化)
    PRCachedURLResponse *cache = [[PRCachedURLResponse alloc] init];
    cache.response = self.response;
    cache.data = self.data;
    [[CWObjectCache sharedCache] storeObject:cache forKey:[[self.request URL] absoluteString]];
}

- (NSURLRequest *)connection:(NSURLConnection *)connection willSendRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)response
{
    if (response) {
        // simply consider redirect as an error
        NSError *error = [NSError errorWithDomain:NSURLErrorDomain code:NSURLErrorResourceUnavailable userInfo:nil];
        [[self client] URLProtocol:self didFailWithError:error];
    }
    return request;
}

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
{
    [[self client] URLProtocol:self didReceiveAuthenticationChallenge:challenge];
}

- (void)connection:(NSURLConnection *)connection didCancelAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
{
    [[self client] URLProtocol:self didCancelAuthenticationChallenge:challenge];
}

@end