Adding initializers via extension in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an extension in Swift?

An extension in Swift adds new functionality to an existing class, struct, enum, or protocol without modifying the original source code.

beginner

Can you add initializers to a struct using an extension in Swift?

Yes, you can add new initializers to a struct using an extension, allowing you to create instances in new ways without changing the original struct definition.

intermediate

Why can't you add designated initializers to a class via extension in Swift?

Swift does not allow adding designated initializers to classes via extensions because it could break the class's initialization rules and safety guarantees.

intermediate

What is the difference between a convenience initializer and a designated initializer in Swift?

A designated initializer fully initializes all properties and calls a superclass initializer. A convenience initializer calls another initializer in the same class and provides a shortcut for common initialization.

beginner

Show a simple example of adding an initializer to a struct using an extension in Swift.

struct Point { var x: Int; var y: Int } extension Point { init(value: Int) { self.x = value self.y = value } } // Now you can create Point(value: 5) to set both x and y to 5.

Which of the following can you add via extension in Swift?

A New initializers to a struct

B Designated initializers to a class

C Stored properties

D Deinitializers

You can add new initializers to structs via extensions, but not designated initializers to classes. Stored properties and deinitializers cannot be added via extensions.

What keyword is used to define an extension in Swift?

A add

B extend

C extension

D include

The keyword 'extension' is used to add new functionality to existing types in Swift.

Why can't you add stored properties in an extension?

A Because stored properties are deprecated

B Because extensions can only add computed properties and methods

C Because Swift does not support extensions

D Because stored properties require memory allocation which extensions can't do

Extensions cannot add stored properties because they require additional memory allocation, which is not allowed in extensions.

Which initializer type can you add to a class via extension?

A Convenience initializer

B Designated initializer

C Deinitializer

D Stored property initializer

You can add convenience initializers to classes via extensions, but not designated initializers.

What happens if you add an initializer in an extension that duplicates an existing initializer?

A The new initializer overrides the old one

B Compilation error due to duplicate initializers

C Both initializers coexist without issues

D The program crashes at runtime

Swift does not allow duplicate initializers with the same signature; this causes a compilation error.

Explain how to add an initializer to a struct using an extension in Swift and why this might be useful.

Think about how extensions let you add new ways to create instances without changing the original struct.

Describe the limitations of adding initializers via extensions for classes in Swift.

Consider Swift's rules about class initialization and safety.