I have some classes defined in Objective-C similar to this:
@interface Type: NSObject {
}
@end
@interface SubType1: Type {
}
@end
@interface SubType2: Type {
}
@end
@interface Parent <T: __kindof Type *> : NSObject
@property (nonatomic, strong) NSArray <T> *anArray;
@property (nonatomic, strong) T anObject;
@end
@interface SubParent1: Parent<SubType1 *> {
}
@end
@interface SubParent2: Parent<SubType2 *> {
}
@end
And I am trying to make a Swift function that can take any subclass of Parent. I tried the following:
func callFunc(parent: Parent<Type>) {
}
callFunc(parent: SubParent1())
And I get the error: Cannot convert value of type 'Parent<SubType1> to expected argument type 'Parent<Type>'
Also tried:
func callFunc<T>(parent: T) where T: Parent<Type>{
}
callFunc(parent: SubParent1())
And I get the error Type of expression is ambiguous without more context.
In general I want a method that can handle any type of sub-parent class (SubParent1, SubParent2) which has a subtype of the parent class type (SubType1, SubType2) since the method only needs to access properties defined on the Parent. Switching the Objective-C classes is not a possible option due to some other limitations so I am looking for a solution that keeps the classes defined in Objective-C. Not sure if possible but if it is possible can I downcast afterwards if the parameter is expected as the Parent?
Later Edit: Also how can I allow a function to return any sub-parent type in Swift for example:
enum AnEnum {
case subParent1(_ : SubParent1)
case subParent2(_ : SubParent2)
func subParent<T: Type>() -> Parent<T>? {
switch self {
case .subParent1(let sub1):
return sub1
case .subParent2(let sub2):
return sub2
}
}
}
The compiler complains about sub1 and sub2 that 'Type of expression is ambiguous without more context'.
You're parameterizing on Parent rather than Type, which the thing you're actually changing. You mean:
func callFunc<T>(parent: Parent<T>) { ... }
While you could explicitly call out T: Type, this isn't really necessary, since Parent already enforces that.