Objective-C在performSelectorOnMainThread中传递带参数的消息：

当传递给@selector的方法有参数时，需要有关语法的帮助。谢谢

//This works
dispatch_async(kBgQueue, ^{ 

 [self performSelectorOnMainThread:@selector(hydrateList) withObject:nil waitUntilDone:YES];   

});



//But what about when the method in the selector has arguments?
//This is incorrect, syntactically
  dispatch_async(kBgQueue, ^{ 

     [self performSelectorOnMainThread:@selector(hydrateListForCategory:self.categorySelected) withObject:nil waitUntilDone:YES];
  });

提示：这就是为什么有“withObject:”部分

提示2：苹果的框架有相当好的文档

提示3：

[self performSelectorOnMainThread:@selector(hydrateListForCategory:) withObject:self.categorySelected waitUntilDone:YES];

---

搜索该方法并阅读文档。

[self performSelectorOnMainThread:@selector(hydrateListForCategory:) withObject:self.categorySelected waitUntilDone:YES];