Structs, Classes & Inheritance

Question 1

Let’s say you have a coordinate that is a constant, you want to save that coordinate as a tuple with values 0, 0 for x and y. How would you do this?

Answer 1

Let coordinate = (x: 0, y: 0)

Question 2

struct Point {
    let x: Int
    let y: Int
}	
What are x and y called?

Answer 2

Stored properties

Question 3

When we create this → let coordinatePoint = Point(x: 2, y: 2) (Point is a struct)
What is that called?

Answer 3

An instance of the struct

Question 4

How do we model data in object oriented programming?

Answer 4

By creating objects that serve as data structures, using Structs and Classes

Question 5

How do you add a comment so that it appears when you option click an object?

Answer 5

///

Question 6

What is a method?

Answer 6

A method is a function associated with a particular type not just any old function.

Question 7

What is an instance method?

Answer 7

A method that can only be called on an instance
let coordinatePoint = Point(x: 2, y: 2)
coordinatePoint.points()

Question 8

What is an initializer?

Answer 8

It’s just a special instance method that sets up our class ready for use.  
It has one purpose, to set up an object ready for use. Basically all the stored properties need to have initial values before it is ready to use.
(When we create an instance, the initializer is what allows the stored properties to appear) example let coordinatePoint = Point(x: 2, y: 2)

Question 9

Why doesn’t a struct need an initializer?

Answer 9

It has a memberwise initializer

Question 10

When there is a value where we can only get a value from it, what kind of property is it?

Answer 10

Read only or a gettable property

Question 11

If we can change the value of this property, what kind of property is it?

Answer 11

A read write or a settable property

Question 12

What is the return statement referred to as?

Answer 12

A control transfer statement

Question 13

TF: Classes generate an automatic member wise initializer to create an instance of the class

Answer 13

False

Question 14

TF: Instance methods should be narrow in scope and carry out a single task

Answer 14

True

Question 15

How do we refer to an instance of a class or a struct from within the definition of the object?

Answer 15

Self

Question 16

Methods that we do not call directly on an instance but help compute the output for another function are informally called

Answer 16

Helper methods

Question 17

When creating objects we can only use primitive types (like String, Int, etc) as the types for stored properties

Answer 17

False

Question 18

What is so important regarding inheritance between a struct and a class?

Answer 18

Class allows inheritance.

Question 19

How do you initialize a subclass?

Answer 19

Provide values for properties of the subclass
Once the subclass is initialized, provide values for properties of the base class

Question 20

When you inherit from one class to the other and you want to set up the initializer, what do you have to do?

Answer 20

Override the previous initializer

Question 21

TF: The properties of the subclass need to have initial values first before we do anything with the superclass?

Answer 21

True

Question 22

TF: An Array is a reference type.

Answer 22

False

Question 23

TF: An Int is a value type.

Answer 23

True

Question 24

TF: A value type is a type whose value is copied when it is assigned to a variable or constant, or when it is passed to a function

Answer 24

True

Question 25

TF: Reference types are not copied when they are assigned to a variable or constant, or when they are passed to a function. Rather than a copy, a reference to the same existing instance is used instead.

Answer 25

True