我想在NSURLSession上创建一个类别.该应用程序编译好,但是当我尝试调用我得到的类别方法
-[__NSCFURLSession doSomething]: unrecognized selector sent to instance 0xbf6b0f0 <unknown>:0: error: -[NSURLSession_UPnPTests testCategory] : -[__NSCFURLSession doSomething]: unrecognized selector sent to instance 0xbf6b0f0
很奇怪,这里是我建立的一个测试类来显示问题. NSString上的类别工作正常,但NSURLSession上的类别在运行时无法找到该方法.我怀疑这是内在的东西.
意见:-)
#import <XCTest/XCTest.h>
@interface NSString (test)
-(void) doSomethingHere;
@end
@implementation NSString (test)
-(void) doSomethingHere {
NSLog(@"Hello string");
}
@end
@interface NSURLSession (test)
-(void) doSomething;
@end
@implementation NSURLSession (test)
-(void) doSomething {
NSLog(@"Hello!!!!");
}
@end
@interface NSURLSession_UPnPTests : XCTestCase
@end
@implementation NSURLSession_UPnPTests
-(void) testCategory {
[@"abc" doSomethingHere];
NSURLSession *session = [NSURLSession sharedSession];
[session doSomething];
}
@end
解决方法
我已经得到了与NSURLSessionUploadTasks相似的结果,它们在-URLSession期间被反序列化为__NSCFURLSessionUploadTasks：task：didCompleteWithError：delegate callback.
如果我是你,我会放弃这种方法,并使用组合(即使NSURLSession成为另一个对象中的ivar).如果您需要使用NSURLSession存储一些信息,可以将JSON编码的字典填入.sessionDescription.
这是我以前为一个任务做的代码：
#pragma mark - Storing an NSDictionary in NSURLSessionTask.description
// This lets us attach some arbitrary information to a NSURLSessionTask by JSON-encoding
// an NSDictionary,and storing it in the .description field.
//
// Attempts at creating subclasses or categories on NSURLSessionTask have not worked out,// because the –URLSession:task:didCompleteWithError: callback passes an
// __NSCFURLSessionUploadTask as the task argument. This is the best solution I could
// come up with to store arbitray info with a task.
- (void)storeDictionary:(NSDictionary *)dict inDescriptionOfTask:(NSURLSessionTask *)task
{
NSData *data = [NSJSONSerialization dataWithJSONObject:dict options:0 error:nil];
NSString *stringRepresentation = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
[task setTaskDescription:stringRepresentation];
[stringRepresentation release];
}
- (NSDictionary *)retrieveDictionaryFromDescriptionOfTask:(NSURLSessionTask *)task
{
NSString *desc = [task taskDescription];
if (![desc length]) {
DDLogError(@"No description for %@",task);
return nil;
}
NSData *data = [desc dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary *dict = (data ? (id)[NSJSONSerialization JSONObjectWithData:data options:0 error:nil] : nil);
if (!dict) {
DDLogError(@"Could not parse dictionary from task %@,description\n%@",task,desc);
}
return dict;
}
