将Swift委托分配给Objective-C对象时出错

这是我的斯威夫特班:

class MyClass : NSObject {
    public var inAppMessagesController: MPInAppMessagesController!

fun myFunction() {
    self.inAppMessagesController.inAppInteractionDelegate = self    // Error in this line - Cannot assign value of type 'MyClass' to type 'MPInAppMessageControllerDelegate?'
}

}  

extension MyClass : MPInAppMessageControllerDelegate {
  // Functions 
}   

如评论中所述,这是一个错误-

'MPInAppMessageControllerDelegate?'

在里面 Objective-C MPinApp消息控制器

@interface MPInAppMessagesController : NSObject

@property (nonatomic, weak, nullable) id <MPInAppMessageControllerDelegate> inAppInteractionDelegate;

@end   

MPInAppMessageControllerDelegate mpinappMessagesControl.h :

@protocol MPInAppMessageControllerDelegate<NSObject>

// Functions

@end