How to call an Objective-C singleton from Swift?

Question

I have an objective-C singleton as follows:

 @interface MyModel : NSObject
    + (MyModel*)   model;
    ...


        + (MyModel*) model 
        {
                     


        

Answer 1

Do exactly what the compiler warning tells you to:

MyModel().someMethod()

Read on to see why...

---

Swift automatically recognizes ObjC conventions for initializers and convenience constructors. If you have a class that looks like this:

@interface XYZThing : NSObject
+ (instancetype)thing;
+ (instancetype)thingWithFoo:(int)foo bar:(int)bar;
@end

...then, when Swift turns them into initializers, it elides the part of the method name that's the generic name of the class (Thing/thing), moves the part of the selector that refers to the parameter to be a parameter label, and drops any prepositions connecting those parts. So the initializer declarations look like this in Swift:

class XYZThing: NSObject [
    init()
    init(foo: Int, bar: Int)
}

and you construct objects like this:

let thing = XYZThing()
let otherThing = XYZThing(foo:3, bar:7)

---

A followup: because class methods like +[XYZThing thing] are treated like initializers by the ObjC to Swift translator (even if that doesn't seem to fully work right now), that naming pattern is a bad idea for singletons. A singleton retrieval method shouldn't be an initializer, because an initializer always creates a new instance.

A singleton retrieval method should instead have a name that doesn't start with the generic name of the class; e.g. +sharedThing, +defaultThing, +oneThingToRuleThemAll, etc.