CODEWITHSUNDEEP
iosswiftfunction
Esqarrouth
Esqarrouth

Reputation: 39181

Difference between class func vs only func

Whats the difference between these 2?

extension UIFont {
    class func PrintFontFamily(font: FontName) {
        let arr = UIFont.fontNamesForFamilyName(font.rawValue)
        for name in arr {
            println(name)
        }
    }
}

extension UIFont {
    func PrintFontFamily(font: FontName) {
        let arr = UIFont.fontNamesForFamilyName(font.rawValue)
        for name in arr {
            println(name)
        }
    }
}

Upvotes: 1

Views: 1515

Answers (5)

Epic Defeater
Epic Defeater

Reputation: 2147

A class func is called on the type itself, while just func is called on the instance of that type.

An example:

class Test {
  func test() {

  }
}

To call test():

Test().test()

Here is the same thing with a class func

class Test {
   class func test() {
   } 
}

To call test():

Test.test()

So, you don't have to make an instance of the class.

You can also call a static func. The difference between a static func and a class func is that static func translates into class final func which just means that subclasses cannot override the function.

Upvotes: 1

Kalenda
Kalenda

Reputation: 1927

"Instance methods are methods that are called on an instance of a particular type. You can also define methods that are called on the type itself. These kinds of methods are called type methods. You indicate type methods by writing the keyword static 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."

Instance method. 

class Counter {
    var count = 0
    func increment() {
        ++count
    }
    func incrementBy(amount: Int) {
        count += amount
    }
    func reset() {
        count = 0
    }
}

Usage: 

let counter = Counter()
// the initial counter value is 0
counter.increment()
// the counter's value is now 1
counter.incrementBy(5)
// the counter's value is now 6
counter.reset()
// the counter's value is now 0

Type methods:

class SomeClass {
    class func someTypeMethod() {
        // type method implementation goes here
    }
}

Usage: 

SomeClass.someTypeMethod()

Upvotes: 3

Greg
Greg

Reputation: 25459

The difference is that you call an class function like this:

UIFont.PrintFontFamily("test")

But 'constructing' the function with just the func keyword require create instance of the class and call the method on that instance:

var myFont = UIFont()
myFont.PrintFontFamily("test")

Upvotes: 3

Dean
Dean

Reputation: 1542

A class function is called with the class :

UIFont.PrintFontFamily("Helvetica Neue")

A non class function is a method you call from an instantiated object :

let font = UIFont(name: "Helvetica Neue", size: 30)
font.PrintFontFamily("Helvetica Neue")

In that case, you should use a class func

Upvotes: 1

matt
matt

Reputation: 534885

A class func is a class method. It is called by sending a message to the class.

A func is an instance method. It is called by sending a message to an instance of the class.

Upvotes: 6

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