Jun 29, 2022
2 min read
Learn Swift Fundamentals by preparing for Job Interview, Questions 133 ~ 138 For Extension
Extensions are really useful. This is the reason I like swift the most. Why don’t other languages include this feature? Personally, extension is in my top 3 reasons to love swift.
133) What is extension?
Answer:
- Way of adding new functionality without subclassing is known as Extension.
class A { func aFunc() { }}extension A {
func bFunc() {
}}let a: A = A()
a.aFunc()
a.bFunc()
134) What is the difference between Subclassing (Inheritance) and Extension?
Answer:
- No overriding in extension
- No stored properties in extension (with computed property though, you can)
- Newly added functionality is available to all instances of that class
class A { func aFunc() { }}extension A {
func bFunc() {
}}let a: A = A()
a.aFunc()
a.bFunc()
135) Can we use stored property in extension?
Answer:
- No
class A {}// Error
extension A {
var b: Int = 3
}
136) Can we use computed property in extension?
Answer:
- Yes, you can declare property with get set
class A {}extension A {
var b: Int {
get {
return 3
}
}
}
137) Can we override existing methods using Extension?
Answer:
- No, overriding the existing functionality is not allowed in Extension.
138) When to choose Extensions over inheritance?
Answer:
- Go for extension when you want to add new functionality that should be available for all instances of that class.
- Go for subclassing when you want to extend the functionality of a class and that should be available for only newly created class. When you want to override the functionality of a class, go for subclassing.
