Objective-C 中不相关对象的语义问题
我有一个 UIViewController 子类，它实现了一条消息以使用自定义模型初始化控制器：
- (id)initWithUser:(FacebookFriend *)user;
当我使用它来初始化我的控制器时：
ProfileViewController *profileViewController = [[ProfileViewController alloc] initWithUser:friend];
编译器抱怨向 NSUserDefaults 发送消息' 同名消息：
- (id)initWithUser:(NSString *)username;
warning: incompatible Objective-C types 'struct FacebookFriend *', expected 'struct NSString *' when passing argument 1 of 'initWithUser:' from distinct Objective-C type
我不太明白为什么它通知我这一点，因为我不认为 UIViewController 继承自任何地方的 NSUserDefaults 。有没有办法禁用这个错误？这会导致问题吗？我应该重命名我的类的初始值设定项以避免混淆吗？
I have a UIViewController subclass that implements a message to init the controller with a custom model:
- (id)initWithUser:(FacebookFriend *)user;
When I use this to init my controller:
ProfileViewController *profileViewController = [[ProfileViewController alloc] initWithUser:friend];
The compiler complains about sending a message to NSUserDefaults' message of the same name:
- (id)initWithUser:(NSString *)username;
warning: incompatible Objective-C types 'struct FacebookFriend *', expected 'struct NSString *' when passing argument 1 of 'initWithUser:' from distinct Objective-C type
I don't quite understand why it's notifying me of this as I don't think UIViewController inherits from NSUserDefaults anywhere. Is there a way to disable this error? Could this cause a problem? Should I just rename my class' initializer to avoid confusion?
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问题是你有一个不明确的选择器。因为
alloc返回通用（对于 Objective C）类型id，所以对initWithUser:的调用变得不明确，因此它与NSUserDefaults方法initWithUser:。编译器认为你正在尝试使用那个。您可以通过强制转换来消除歧义：
The problem is you have an ambiguous selector. Because
allocreturns the generic (for Objective C) typeid, the call toinitWithUser:has become ambiguous, and so it gets confused with theNSUserDefaultsmethodinitWithUser:. The compiler thinks you're trying to use that one.You can remove the ambiguity by casting:
您是否尝试过直接转换
-alloc的结果？像这样的东西：Have you tried directly casting the result of
-alloc? Something like this: