1 // AFHTTPRequestOperation.m
  2 //
  3 // Copyright (c) 2013-2014 AFNetworking (http://afnetworking.com)
  4 //
  5 // Permission is hereby granted, free of charge, to any person obtaining a copy
  6 // of this software and associated documentation files (the "Software"), to deal
  7 // in the Software without restriction, including without limitation the rights
  8 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  9 // copies of the Software, and to permit persons to whom the Software is
 10 // furnished to do so, subject to the following conditions:
 11 //
 12 // The above copyright notice and this permission notice shall be included in
 13 // all copies or substantial portions of the Software.
 14 //
 15 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 16 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 17 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 18 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 19 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 20 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 21 // THE SOFTWARE.
 22  
 23 #import "AFHTTPRequestOperation.h"
 24  
 25 static dispatch_queue_t http_request_operation_processing_queue() {
 26 static dispatch_queue_t af_http_request_operation_processing_queue;
 27 static dispatch_once_t onceToken;
 28 dispatch_once(&onceToken, ^{
 29 af_http_request_operation_processing_queue = dispatch_queue_create("com.alamofire.networking.http-request.processing", DISPATCH_QUEUE_CONCURRENT);
 30 });
 31  
 32 return af_http_request_operation_processing_queue;
 33 }
 34  
 35 static dispatch_group_t http_request_operation_completion_group() {
 36 static dispatch_group_t af_http_request_operation_completion_group;
 37 static dispatch_once_t onceToken;
 38 dispatch_once(&onceToken, ^{
 39 af_http_request_operation_completion_group = dispatch_group_create();
 40 });
 41  
 42 return af_http_request_operation_completion_group;
 43 }
 44  
 45 #pragma mark -
 46  
 47 @interface AFURLConnectionOperation ()
 48 @property (readwrite, nonatomic, strong) NSURLRequest *request;
 49 @property (readwrite, nonatomic, strong) NSURLResponse *response;
 50 @end
 51  
 52 @interface AFHTTPRequestOperation ()
 53 @property (readwrite, nonatomic, strong) NSHTTPURLResponse *response;
 54 @property (readwrite, nonatomic, strong) id responseObject;
 55 @property (readwrite, nonatomic, strong) NSError *responseSerializationError;
 56 @property (readwrite, nonatomic, strong) NSRecursiveLock *lock;
 57 @end
 58  
 59 @implementation AFHTTPRequestOperation
 60 @dynamic lock;
 61  
 62 - (instancetype)initWithRequest:(NSURLRequest *)urlRequest {
 63 self = [super initWithRequest:urlRequest];
 64 if (!self) {
 65 return nil;
 66 }
 67 //默认使用AFHTTPResponseSerializer，只能解析错误信息
 68 self.responseSerializer = [AFHTTPResponseSerializer serializer];
 69  
 70 return self;
 71 }
 72  
 73 - (void)setResponseSerializer:(AFHTTPResponseSerializer  *)responseSerializer {
 74 NSParameterAssert(responseSerializer);
 75  
 76 [self.lock lock];
 77 _responseSerializer = responseSerializer;
 78 self.responseObject = nil;
 79 self.responseSerializationError = nil;
 80 [self.lock unlock];
 81 }
 82  
 83 - (id)responseObject {
 84 [self.lock lock];
 85 //第一次读取时用responseSerializer解析数据，生成responseObject
 86 if (!_responseObject && [self isFinished] && !self.error) {
 87 NSError *error = nil;
 88 self.responseObject = [self.responseSerializer responseObjectForResponse:self.response data:self.responseData error:&error];
 89 if (error) {
 90 self.responseSerializationError = error;
 91 }
 92 }
 93 [self.lock unlock];
 94  
 95 return _responseObject;
 96 }
 97  
 98 - (NSError *)error {
 99 if (_responseSerializationError) {
100 return _responseSerializationError;
101 } else {
102 return [super error];
103 }
104 }
105  
106 #pragma mark - AFHTTPRequestOperation
107  
108 - (void)setCompletionBlockWithSuccess:(void (^)(AFHTTPRequestOperation *operation, id responseObject))success
109 failure:(void (^)(AFHTTPRequestOperation *operation, NSError *error))failure
110 {
111 // completionBlock is manually nilled out in AFURLConnectionOperation to break the retain cycle.
112 //父类setCompletionBlock的实现里解决了循环引用问题，这里在block里直接用self也没问题
113 //不过编译器会警告retain-cycles，所以得加-Warc-retain-cycles
114 #pragma clang diagnostic push
115 #pragma clang diagnostic ignored "-Warc-retain-cycles"
116 #pragma clang diagnostic ignored "-Wgnu"
117 self.completionBlock = ^{
118 //这里又让回调在group里运行，感觉为了加group，下面这些代码可读性低了点，跟父类的setCompletionBlock一样，看不出这个group的作用。
119 if (self.completionGroup) {
120 dispatch_group_enter(self.completionGroup);
121 }
122  
123 dispatch_async(http_request_operation_processing_queue(), ^{
124 if (self.error) {
125 if (failure) {
126 dispatch_group_async(self.completionGroup ?: http_request_operation_completion_group(), self.completionQueue ?: dispatch_get_main_queue(), ^{
127                         //默认回调到主线程，下同
128 failure(self, self.error);
129 });
130 }
131 } else {
132 id responseObject = self.responseObject;
133 //第一次读取self.responseObject时会构建responseObject，构建过程中可能会出现错误，所以这里继续判断self.error是否有错误
134 if (self.error) {
135 if (failure) {
136 dispatch_group_async(self.completionGroup ?: http_request_operation_completion_group(), self.completionQueue ?: dispatch_get_main_queue(), ^{
137 failure(self, self.error);
138 });
139 }
140 } else {
141 if (success) {
142 dispatch_group_async(self.completionGroup ?: http_request_operation_completion_group(), self.completionQueue ?: dispatch_get_main_queue(), ^{
143 success(self, responseObject);
144 });
145 }
146 }
147 }
148  
149 if (self.completionGroup) {
150 dispatch_group_leave(self.completionGroup);
151 }
152 });
153 };
154 #pragma clang diagnostic pop
155 }
156  
157 #pragma mark - AFURLRequestOperation
158 //下载暂停时提供断点续传功能，修改请求的HTTP头，记录当前下载的文件位置，下次可以从这个位置开始下载。
159 - (void)pause {
160 [super pause];
161  
162 u_int64_t offset = 0;
163 if ([self.outputStream propertyForKey:NSStreamFileCurrentOffsetKey]) {
164 offset = [(NSNumber *)[self.outputStream propertyForKey:NSStreamFileCurrentOffsetKey] unsignedLongLongValue];
165 } else {
166 offset = [(NSData *)[self.outputStream propertyForKey:NSStreamDataWrittenToMemoryStreamKey] length];
167 }
168  
169 NSMutableURLRequest *mutableURLRequest = [self.request mutableCopy];
170 if ([self.response respondsToSelector:@selector(allHeaderFields)] && [[self.response allHeaderFields] valueForKey:@"ETag"]) {
171 //若请求返回的头部有ETag，则续传时要带上这个ETag，ETag用于放置文件的唯一标识，比如文件MD5值
172 //续传时带上ETag服务端可以校验相对上次请求，文件有没有变化，若有变化则返回200，回应新文件的全数据，若无变化则返回206续传。
173 [mutableURLRequest setValue:[[self.response allHeaderFields] valueForKey:@"ETag"] forHTTPHeaderField:@"If-Range"];
174 }
175 //给当前request加Range头部，下次请求带上头部，可以从offset位置继续下载
176 [mutableURLRequest setValue:[NSString stringWithFormat:@"bytes=%llu-", offset] forHTTPHeaderField:@"Range"];
177 self.request = mutableURLRequest;
178 }
179  
180 #pragma mark - NSSecureCoding
181  
182 + (BOOL)supportsSecureCoding {
183 return YES;
184 }
185  
186 - (id)initWithCoder:(NSCoder *)decoder {
187 self = [super initWithCoder:decoder];
188 if (!self) {
189 return nil;
190 }
191  
192 self.responseSerializer = [decoder decodeObjectOfClass:[AFHTTPResponseSerializer class] forKey:NSStringFromSelector(@selector(responseSerializer))];
193  
194 return self;
195 }
196  
197 - (void)encodeWithCoder:(NSCoder *)coder {
198 [super encodeWithCoder:coder];
199  
200 [coder encodeObject:self.responseSerializer forKey:NSStringFromSelector(@selector(responseSerializer))];
201 }
202  
203 #pragma mark - NSCopying
204  
205 - (id)copyWithZone:(NSZone *)zone {
206 AFHTTPRequestOperation *operation = [super copyWithZone:zone];
207  
208 operation.responseSerializer = [self.responseSerializer copyWithZone:zone];
209 operation.completionQueue = self.completionQueue;
210 operation.completionGroup = self.completionGroup;
211  
212 return operation;
213 }
214  
215 @end