iOS AFNetworking取消网络请求

@propert(noatomic, strong) AFURLSessionManager *manager;
//懒加载
//code...

-(void)loadNew
{
  //结束之前的所有请求
  [self.manager.tasks makeObjectsPerformSelector:@selector(cancel)];
  //网络请求
  //code...
}

//点击返回按钮用
-(void)delloc
{
  [self.manager invalidateSessionCancelingTasks:YES];
}