Child classes can replace parent methods with their own implementations – a process known as overriding. Here’s a trivial Dog
class with a makeNoise()
method:
class Dog {
func makeNoise() {
print("Woof!")
}
}
If we create a new Poodle
class that inherits from Dog
, it will inherit the makeNoise()
method. So, this will print “Woof!”:
class Poodle: Dog {
}
let poppy = Poodle()
poppy.makeNoise()
Method overriding allows us to change the implementation of makeNoise()
for the Poodle
class.
Swift requires us to use override func
rather than just func
when overriding a method – it stops you from overriding a method by accident, and you’ll get an error if you try to override something that doesn’t exist on the parent class:
class Poodle: Dog {
override func makeNoise() {
print("Yip!")
}
}
With that change, poppy.makeNoise()
will print “Yip!” rather than “Woof!”.
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