CODEWITHSUNDEEP
objective-cswift
henryeverett
henryeverett

Reputation: 803

Overriding an Obj-c class function in Swift

Either I'm seeing some strange behaviour from Swift or I'm doing something wrong.

Let's say you have an obj-c class called TurtleHelper which looks like this:

@interface TurtleHelper : NSObject

+(NSDictionary*)getTurtles;

@end

Then I want to override this method in Swift, so I do this:

class SwiftTurtles: TurtleHelper {

    override class func getTurtles() -> NSDictionary {
        // ...
    }
}

The compiler throws the following error at me:

Overriding method with selector getTurtles has incompatible type () -> NSDictionary

What am I doing wrong?

Upvotes: 5

Views: 2171

Answers (2)

leandrodemarco
leandrodemarco

Reputation: 1562

I had a very similar issue. Using XCode 12.2 I tried to override a function quite alike:

@interface AuthService : NSObject
- (NSDictionary *)authHeaders;
@end

I tried to subclass it as in the above answer and a lot of optional, implictly unwrapped, bridged classes combinations, but what ended up working for me (Swift 4.2, XCode 12.2) was

class AuthServiceMock: AuthService {
    override func authHeaders() -> [AnyHashable: Any]?
}

Upvotes: 0

henryeverett
henryeverett

Reputation: 803

It turns out that the answer seems to be

override class func getTurtles() -> [NSObject : AnyObject]!

From Apple's documentation:

When you bridge from an NSDictionary object to a Swift dictionary, the resulting dictionary is of type [NSObject: AnyObject]. You can bridge any NSDictionary object to a Swift dictionary because all Objective-C objects are AnyObject compatible.

Reference: https://developer.apple.com/library/prerelease/mac/documentation/Swift/Conceptual/BuildingCocoaApps/WorkingWithCocoaDataTypes.html

Upvotes: 8

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