在看afnetworking的源码,
发现在AFURLConnectionOperation中实现了NSCoding, NSCopying这两个协议,实现这两个协议的作用是什么?
在什么情况下会用到这些方法?
版本是2.6.1
#pragma mark - NSCoding - (id)initWithCoder:(NSCoder *)aDecoder { NSURLRequest *request = [aDecoder decodeObjectForKey:@"request"]; self = [self initWithRequest:request]; if (!self) { return nil; } self.state = [aDecoder decodeIntegerForKey:@"state"]; self.cancelled = [aDecoder decodeBoolForKey:@"isCancelled"]; self.response = [aDecoder decodeObjectForKey:@"response"]; self.error = [aDecoder decodeObjectForKey:@"error"]; self.responseData = [aDecoder decodeObjectForKey:@"responseData"]; self.totalBytesRead = [[aDecoder decodeObjectForKey:@"totalBytesRead"] longLongValue]; return self; } - (void)encodeWithCoder:(NSCoder *)aCoder { [self pause]; [aCoder encodeObject:self.request forKey:@"request"]; switch (self.state) { case AFOperationExecutingState: case AFOperationPausedState: [aCoder encodeInteger:AFOperationReadyState forKey:@"state"]; break; default: [aCoder encodeInteger:self.state forKey:@"state"]; break; } [aCoder encodeBool:[self isCancelled] forKey:@"isCancelled"]; [aCoder encodeObject:self.response forKey:@"response"]; [aCoder encodeObject:self.error forKey:@"error"]; [aCoder encodeObject:self.responseData forKey:@"responseData"]; [aCoder encodeObject:[NSNumber numberWithLongLong:self.totalBytesRead] forKey:@"totalBytesRead"]; } #pragma mark - NSCopying - (id)copyWithZone:(NSZone *)zone { AFURLConnectionOperation *operation = [[[self class] allocWithZone:zone] initWithRequest:self.request]; operation.uploadProgress = self.uploadProgress; operation.downloadProgress = self.downloadProgress; operation.authenticationAgainstProtectionSpace = self.authenticationAgainstProtectionSpace; operation.authenticationChallenge = self.authenticationChallenge; operation.cacheResponse = self.cacheResponse; operation.redirectResponse = self.redirectResponse; return operation; }
即使是新的3.0版本
在AFHTTPSessionManager里也是实现了这两个协议
- (instancetype)initWithCoder:(NSCoder *)decoder { NSURL *baseURL = [decoder decodeObjectOfClass:[NSURL class] forKey:NSStringFromSelector(@selector(baseURL))]; NSURLSessionConfiguration *configuration = [decoder decodeObjectOfClass:[NSURLSessionConfiguration class] forKey:@"sessionConfiguration"]; if (!configuration) { NSString *configurationIdentifier = [decoder decodeObjectOfClass:[NSString class] forKey:@"identifier"]; if (configurationIdentifier) { #if (defined(__IPHONE_OS_VERSION_MIN_REQUIRED) && __IPHONE_OS_VERSION_MIN_REQUIRED >= 80000) || (defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && __MAC_OS_X_VERSION_MIN_REQUIRED >= 1100) configuration = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:configurationIdentifier]; #else configuration = [NSURLSessionConfiguration backgroundSessionConfiguration:configurationIdentifier]; #endif } } self = [self initWithBaseURL:baseURL sessionConfiguration:configuration]; if (!self) { return nil; } self.requestSerializer = [decoder decodeObjectOfClass:[AFHTTPRequestSerializer class] forKey:NSStringFromSelector(@selector(requestSerializer))]; self.responseSerializer = [decoder decodeObjectOfClass:[AFHTTPResponseSerializer class] forKey:NSStringFromSelector(@selector(responseSerializer))]; AFSecurityPolicy *decodedPolicy = [decoder decodeObjectOfClass:[AFSecurityPolicy class] forKey:NSStringFromSelector(@selector(securityPolicy))]; if (decodedPolicy) { self.securityPolicy = decodedPolicy; } return self; } - (void)encodeWithCoder:(NSCoder *)coder { [super encodeWithCoder:coder]; [coder encodeObject:self.baseURL forKey:NSStringFromSelector(@selector(baseURL))]; if ([self.session.configuration conformsToProtocol:@protocol(NSCoding)]) { [coder encodeObject:self.session.configuration forKey:@"sessionConfiguration"]; } else { [coder encodeObject:self.session.configuration.identifier forKey:@"identifier"]; } [coder encodeObject:self.requestSerializer forKey:NSStringFromSelector(@selector(requestSerializer))]; [coder encodeObject:self.responseSerializer forKey:NSStringFromSelector(@selector(responseSerializer))]; [coder encodeObject:self.securityPolicy forKey:NSStringFromSelector(@selector(securityPolicy))]; } #pragma mark - NSCopying - (instancetype)copyWithZone:(NSZone *)zone { AFHTTPSessionManager *HTTPClient = [[[self class] allocWithZone:zone] initWithBaseURL:self.baseURL sessionConfiguration:self.session.configuration]; HTTPClient.requestSerializer = [self.requestSerializer copyWithZone:zone]; HTTPClient.responseSerializer = [self.responseSerializer copyWithZone:zone]; HTTPClient.securityPolicy = [self.securityPolicy copyWithZone:zone]; return HTTPClient; }
NSCoding, NSCopying 协议,是整个Objective-C中比较重要的两个协议。
前者,是编码协议,后者是拷贝协议。
AFURLConnectionOperation
实现NSCoding
以后,可以通过NSKeyedArchiver
类进行数据序列化,简单说就是将AFURLConnectionOperation
对象转成NSData
,方便写入数据库或者文件,下次使用使用NSUnKeyedArchiver
进行反序列化,就可以得到相同的实例。
NSCopying
就更常用了。实现拷贝用的,比如
AFURLConnectionOperation* c = [AFURLConnectionOperation new]; AFURLConnectionOperation* d = [c copy]; 这个时候 c 和 d 是不同的对象,d是c的拷贝。
NSCoding肯定是为了持久化的。
比如下载视频之类的大文件,没下载完的时候app被kill掉了,这个时候就可以把Operation持久化,下次再读出来直接发送就ok了。