Extensions

Question 1

TF: You can add computed properties to extensions?

Answer 1

True

Question 2

TF: You can add stored properties or property observers?

Answer 2

False

Question 3

TF: You can add new type and instance methods.

Answer 3

True

Question 4

TF: You can define nested types

Answer 4

True

Question 5

TF: Can add convenience initializers

Answer 5

True

Question 6

TF: We can add protocol conformance to both custom types, native types and types from external frameworks in an extension

Answer 6

True

Question 7

TF:You cannot provide a default implementation for any requirements specified in a protocol

Answer 7

False

Question 8

TF: We can only provide default implementations for protocols via an extension.

Answer 8

True

Question 9

What’s the purpose of using an Extension?

Answer 9

Extensions add new functionality to an existing class, structure, enumeration, or protocol type.

Question 10

TF: Extensions can add new functionality to a type, but they cannot override existing functionality.

Answer 10

True

Question 11

protocol SomeProtocol {
    func someMethod() -> Int
}

extension SomeProtocol {
    func someMethod() -> Int {
        return 1
    }
}

struct SomeStruct: SomeProtocol {
    func someMethod() -> Int {
        return 2
    }
}

let b: SomeProtocol = SomeStruct()
b.someMethod()

What is the value returned from the someMethod() call?

Answer 11

1

Question 12

Why can we not add designated initializers in a class extension?

Answer 12

A designated initializer initializes all properties of a class and we don't have access to private properties in an extension
A designated initializer needs to call a specific superclass' initializer which is not possible from the extension.

Question 13

protocol SomeProtocol {
    func someMethod() -> Int
}

extension SomeProtocol {
    func someMethod() -> Int {
        return 1
    }
}

struct SomeStruct: SomeProtocol {
    func someMethod() -> Int {
        return 2
    }
}

let a: SomeStruct = SomeStruct()
a.someMethod()

What is the value returned from the someMethod() call

Answer 13

2

Question 14

Which of following is not allowed in an extension? (Instance Methods, Stored Properties, Type Methods, Computed Properties)

Answer 14

Stored Properties