Question

我正在尝试为NSURLProtocol创建一个子类。但是，我注意到，当我注册我的子类时，我似乎失去了缓存功能，即使它不应该做任何事情。例如，如果我在不注册子类的情况下多次[NSURLConnection sendSynchronousRequest ...]到同一个URL，它只执行一个实际的http请求。注册此子类后，它每次都会执行网络请求。

这是我的代码：

@interface CustomURLProtocol : NSURLProtocol
@property (nonatomic, strong) NSURLConnection *connection;
@end

@implementation CustomURLProtocol

+ (BOOL)canInitWithRequest:(NSURLRequest *)request {
    return [[[request URL] scheme] isEqualToString:@"http"] &&
           [NSURLProtocol propertyForKey:@"tagged" inRequest:request] == nil;
}

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

- (void)startLoading {
    NSMutableURLRequest *newRequest = [self.request mutableCopy];
    [NSURLProtocol setProperty:@YES forKey:@"tagged" inRequest:newRequest];
    self.connection = [NSURLConnection connectionWithRequest:newRequest delegate:self];
}

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

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    [[self client] URLProtocol:self didLoadData:data];
}

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

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    [[self client] URLProtocol:self didReceiveResponse:response cacheStoragePolicy:[[self request] cachePolicy]];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection  {
    [[self client] URLProtocolDidFinishLoading:self];
    self.connection = nil;
}
@end

Answer 1

这里的问题不是我的预期。真正的问题是重定向没有得到正确处理，因为以下代码不存在：

- (NSURLRequest *)connection:(NSURLConnection *)connection willSendRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)response {
  [[self client] URLProtocol:self wasRedirectedToRequest:request redirectResponse:response];
  return request;
}

如果没有此代码，重定向不会被缓存，因此请求对重定向的网址（如wikipedia.com）的顺序请求每次都会导致重定向。

Answer 2

我认为您添加的行只是跳过您的自定义NSURLProtocol。添加此方法后，是否还在调用那些connectionDelegate方法？

更新：终于弄明白了。这就是原因。将此部件添加到startLoading后，我将其工作。

NSCachedURLResponse *cachedResponse = [[NSURLCache sharedURLCache] cachedResponseForRequest:self.request];
    if (cachedResponse) {  
        [self connection:nil didReceiveResponse:[cachedResponse response]];
        [self connection:nil didReceiveData:[cachedResponse data]];
        [self connectionDidFinishLoading:nil];
    } else {
        _connection = [NSURLConnection connectionWithRequest:newRequest delegate:self];
    }

缓存无法使用自定义NSURLProtocol

2 个答案: