Extensions

Question 1

You can use 1._____ to add functionality to an existing type, such as new 2.____ and 3.______ _______

Answer 1

1. extension 2. methods 3. computed properties

Question 2

You can use 1. ______ to add protocol conformance to a type that is declared 2. ______ or even a 3. _____ that you imported from a 4._____ or 5. ______

Answer 2

1. extension 2. elsewhere 3. type 4. library 5. Framework

Question 3

What do “extensions” do?

Answer 3

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

Question 4

What is retroactive modeling?

Answer 4

The ability to extend types for which you do not have access to the original source code. Extensions include retroactive modeling.

Question 5

Extensions are similar to _____ in Objective-C.

Answer 5

categories

Question 6

Unlike Objective-C categories, Swift extensions do not have _____.

Answer 6

names

Question 7

What are six things that extensions in Swift can do?

Answer 7

1. Add computed instance properties and computed type properties
2. Define instance methods and type methods
3. Provide new initializers
4. Define subscripts
5. Define and use new nested types
6. Make an existing type conform to a protocol

Question 8

Extensions can add new functionality to a type, but they can not _____ ______ ______.

Answer 8

Override existing functionality

Question 9

We can declare extensions with the ______ ______.

Answer 9

extension keyword

Question 10

Syntax to declare extension with the extension keyword

Answer 10

extension SomeType {
   //   new functionality to add to SomeType goes here
}

Question 11

An extension can extend an existing type to make it adopt one or more _______.

Answer 11

protocols

Question 12

How do you add protocol conformance when declaring an extension?

Answer 12

You write the protocol names the same way as you would write them for a class or structure.

Question 13

Syntax for an extension that extends an existing type to make it adopt multiple protocols

Answer 13

extension SomeType: SomeProtocol, AnotherProtocol {
   // implementation of protocol requirements goes here
}

Question 14

If you define an extension to add new functionality to an existing type, where will this new functionality be available?

Answer 14

It will be available on all existing instances of that type, even if they were created before the extension was defined.

Question 15

An extension can be used to extend an existing generic type. You can also extend a generic type to _____ ______ ______.

Answer 15

Conditionally add functionality

Question 16

Extensions can add computed 1. ______ properties and computed 2.______ properties to existing types.

Answer 16

1. instance 2. type

Question 17

Extensions can add new computed properties, but they can not add 1. _____ ______, or add 2. _____ _____ to existing properties.

Answer 17

1. stored properties

2. property observers

Question 18

Extensions can add new initializers to existing types. What does this enable you to do? (List 2 things)

Answer 18

1. To extend other types to accept your own custom types as initializer parameters
2. To provide additional initialization options that were not included as part of the type’s original implementation.

Question 19

Extensions can add new convenience initializers to a class, but they can’t add new 1. _____ ______ or 2. _____ to a class.

Answer 19

1. Designated initializers

2. Deinitializers

Question 20

Designated initializers and deinitializers must always be provided by the ____ _____ _____

Answer 20

original class implementation