xcode 从不兼容的类型“ViewController *const__strong”分配给“id<UINavigationControllerDelegate,UIImagePickerControllerDelegate>”
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Assigning to 'id<UINavigationControllerDelegate,UIImagePickerControllerDelegate>' from incompatible type 'ViewController *const__strong'
提问by ???
I have an ImagePickerController in my application.
It works well, but beside ipc.delegate = self;there appears an error message:
我的应用程序中有一个 ImagePickerController。它运行良好，但旁边ipc.delegate = self;出现了一条错误消息：
Assigning to 'id' from incompatible type 'ViewController *const__strong'
从不兼容的类型“ViewController *const__strong”分配给“id”
The app workes well, so I ignored the error message, but I think I need to know why. Why is the error message appearing?
该应用程序运行良好，因此我忽略了错误消息，但我想我需要知道原因。为什么会出现错误信息？
ipc = [[UIImagePickerController alloc]init];
ipc.modalPresentationStyle = UIModalPresentationCurrentContext;
ipc.delegate = self;
ipc.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
[ipc setAllowsEditing:NO];
[self presentViewController:ipc animated:NO completion:nil];
回答by memmons
If you take a look at the definition of the UIImagePickerControllerdelegate property, you'll see it defined as:
如果您查看UIImagePickerController委托属性的定义，您会看到它被定义为：
@property(nonatomic, assign) id<UINavigationControllerDelegate,
UIImagePickerControllerDelegate> delegate
Whatever object you set as the delegate (in this case you are using self) must conform to both the UINavigationControllerDelegateprotocol and the UIImagePickerControllerDelegateprotocol. If the object does not conform to both of these protocols, you'll get a compile-time warning.
无论您设置为委托的任何对象（在本例中您正在使用self）都必须符合UINavigationControllerDelegate协议和UIImagePickerControllerDelegate协议。如果对象不符合这两种协议，您将收到编译时警告。
Here's how you declare that your class conforms to the protocols:
以下是您如何声明您的类符合协议：
@interface MyViewController : UIViewController <UINavigationControllerDelegate,
UIImagePickerControllerDelegate>
Read up on working with protocols, UINavigationControllerDelegate, and UIImagePickerControllerDelegate.
阅读使用协议、UINavigationControllerDelegate和UIImagePickerControllerDelegate。
回答by Armand
I just ran into this for the first time. If your class extends another class which conforms to other protocols, and your class also conforms to these two protocols <UINavigationControllerDelegate, UIImagePickerControllerDelegate>then in order to remove the warning, you must cast it, like this:
我只是第一次遇到这个。如果您的类扩展了另一个符合其他协议的类，并且您的类也符合这两个协议，<UINavigationControllerDelegate, UIImagePickerControllerDelegate>那么为了删除警告，您必须强制转换它，如下所示：
ipc.delegate = (id<<UINavigationControllerDelegate, UIImagePickerControllerDelegate>) self;
Personally, I think this is a bug in the compiler, in that you do adhere to both protocols, you just also happen to adhere to others. Therefore, you shouldn't have to see the warning.
就个人而言，我认为这是编译器中的一个错误，因为您确实遵守了这两种协议，但您也恰好遵守了其他协议。因此，您不应该看到警告。
