How can I create a static class in Swift?

Question

I'm looking to create a static class called VectorCalculator. Perhaps this function should just be placed in my Vector class (similar to NSString's --stringByAppendingString method in Obj-C)... and if you think that... let me know.

Anyway I want to add a couple of static functions to a static class called VectorCalculator. It will calculate the 'dot product' and return a Vector. Another function will likely be to 'calculate and return the angle between two given vectors'.

A) Would anyone go this route of creating a static class for this or

B) should I just add these functions as instance functions of the Vector class such as... public func dotProductWithVector(v: Vector) -> Vector and public func angleWithVector(v: Vector) -> Double. And then both of these argument vectors v will be applied to the Vector classes main Vector u.

What's the benefit of going either A or B?

If you think B, just for future reference, how would you create an all static class in Swift?

I'm very confused with your approach. Why do u need static classes here . — Kumar KL, Jan 25 '16 at 12:36
R u looking for similar to singleton class - thread safe?, but for your req ther is no point of using it. **OR** Class level methods ? — Kumar KL, Jan 25 '16 at 12:38
@KumarKL would you just add these as instance methods of the Vector class then? — chris P, Jan 25 '16 at 12:41
There are no _static classes_ in Swift. What you are talking about is called _static methods_. Concerning your question: both approaches are possible. However, in your case I would go with structs and not classes because Vector is essentially a value type. Further on, you are probably better off with operators defined for such vectors. — 0x416e746f6e, Jan 25 '16 at 12:43
@AntonBronnikov how can you define such operators that you suggest on a vector strict? Thanks. — chris P, Jan 25 '16 at 13:12

score 22 · Answer 1 · answered Mar 03 '17 at 01:29

how would you create an all static class in Swift?

static means no instance, so I would make it a struct with no initializer:

struct VectorCalculator {
    @available(*, unavailable) private init() {}

    static func dotProduct(v: Vector, w: Vector) -> Vector {
        ...
    }
}

curious · Accepted Answer · 2016-01-25T15:06:48.990

16

If I've understood you correctly you are interested in Type methods in case A. You indicate type methods by writing the static keyword before the method’s func keyword. Classes may also use the class keyword to allow subclasses to override the superclass’s implementation of that method. (c)

    struct Vector {
        var x, y, z: Int
    }

    class VectorCalculator {
        static func dotProductOfVector(vec1: Vector, withVector vec2: Vector) -> Vector {
            let newX = //calc x coord;
            let newY = //calc y coord;;
            let newZ = ////calc z coord;;
            return Vector(x: newX,y: newY, z: newZ);
        }
    }

let vec1 = Vector(x:1, y:2, z:3)
let vec2 = Vector(x:4, y:5, z:6)
let v = VectorCalculator.dotProductOfVector(vec1, withVector: vec2)

As for benefits of B it depends on tasks you solve. If you want to left original vectors unmodified it's more convenient to use A variant. But I think you could provide both types of functionality.

edited Jan 25 '16 at 15:06

answered Jan 25 '16 at 12:51

curious

666
4
13

thanks! Can you explain this bit of swift syntax... '(_: Vector, )' ? – chris P Jan 25 '16 at 13:10
@chrisP Sure. Actually this declaration was not correct, therefore I've edited my answer. In order to be able to use passed parameter in method's body, parameter should have local parameter name e.g. `func method(localNameFirst: Vector, localNameSecond: Vector){}`. There are also External parameters. They are just like labels that increase readability of your code. In my answer this label(external parameter) is _withVector_. It is explained [here](http://example.com) in section "Local and External Parameter Names for Methods". – curious Jan 25 '16 at 15:06
@curious This i wrong or Swift changed about that? If you have only one name of a parameter, it acts as internal and external name, making your first argument a required named parameter of the function: `VectorCalculator.dotProductOfVector(vec1: vec1, withVector: vec2)` To allow the first parameter not to be named, you have to declare the argument in the function header like so: `static func dotProductOfVector(_ vec1: Vector, withVector vec2: Vector) -> Vector`. Maybe Swift got changed about that? I'm still learning, but this seems to be the correct way when trying things out. – Martin Braun Jan 23 '18 at 12:15

score 3 · Answer 3 · edited May 23 '17 at 12:10

I think what you looking for are class functions? Maybe your Answer can be found here. How do I declare a class level function in Swift?

class Foo {
    class func Bar() -> String {
       return "Bar"
    }
}

Foo.Bar()

In Swift 2.0 you can use the static keyword instead of class. But you should use static keyword for structs and class keyword for classes

//Edit just saw that i properly misunderstood your question

How can I create a static class in Swift?

3 Answers3

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