Initializers in swift part-3: Required Initializers in swift

Required initializers will be explained in this article.

Here is the first part of this article series: Initializers in swift part-1 : (intro, convenience and designated intializers)

Here is the second part: Initializers in swift part-2: Failable Initializers in swift

Write the required modifier before the definition of a class initializer to indicate that every subclass of the class must implement that initializer.

You must also write the required modifier before every subclass implementation of a required initializer, to indicate that the initializer requirement applies to further subclasses in the chain. You do not write the override modifier when overriding a required designated initializer:

Consider the following example:

//required init
class classA {
required init() {
var a = 10
print(a)
}
}
class classB: classA {
required init() {
var b = 30
print(b)
}
}
//______________________
let objA = classA()
let objB = classB()
prints:
10
30
10
//______________________

Let there be another class classC .

class classC: classA { }
//______________________
let objC = classC() // prints 10 ..superclass init method gets called.

Note: You do not have to provide an explicit implementation of a required initializer if you can satisfy the requirement with an inherited initializer. In the above class classC , since we don’t have any stored properties unintialized at the time of initialization, we dont have to declare the required init explicitly.

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