Properties

Question 1

Type Properties:

If you want to have create a struct named LevelTracker with a single constant type property maxLevel, what must you include in the struct?

Answer 1

Static 
static let maxLevel = 1

Question 2

Type Properties:

What are type properties?

Answer 2

struct Point {
var x: Int = 0
var y: Int = 0
}

struct Map {
    static var origin = Point(x: 1, y: 1)
}
Map.origin = Point(x: 2, y: 2)

So basically there will only be one copy of this property, no matter how many instances of that type you create.

Question 3

Computed Properties:

What is the difference between stored and computed properties?

Answer 3

Stored properties store constant and variable values as part of an instance.
- let length: Int

Computed properties calculate a value instead of storing it
var area: Int {
return length * width
}

Question 4

Computed Properties:

For the area property, this is a read only property. If you wanted to make it a read and right property, what would you have to use?

Answer 4

Get and set

Question 5

If we don’t specify a constant to bind the value in a computed property’s setter, it is automatically bound to a variable named

Answer 5

newValue

Question 6

Type properties are associated with the?

Answer 6

Type itself

Question 7

A computed property that does not specify a getter or setter is by default a

Answer 7

Read only computed property

Question 8

Lazy Stored Properties:

What is a lazy stored property?

Answer 8

A property whose initial value is not calculated until the first time we use it.
Basically, it makes sure no computational power is wasted until it is used.

Question 9

Lazy Stored Properties:

Why does a lazy stored property have to be stored as a var?

Answer 9

Because it might change when you eventually decide to use it.

Question 10

Lazy Stored Properties:

What is the value of a lazy stored property before it is defined?

Answer 10

It does not have a value

Question 11

Property Observers:

What do property observers do?

Answer 11

Property observers allow us to observe and respond to changes in property values.

Question 12

Property Observers:

What are 2 examples of property observers?

Answer 12

willset and didset are property observers. - they allow us to observe changes in a properties value

willSet {
print(“Old value: (value)”)
}

    didSet {
        view.alpha = CGFloat(value)
        print("New value: \(value)")
    }

Question 13

Property Observers:

When are willSet and didSet called?

Answer 13

didSet is executed after the value has been assigned.

willSet is called before the underlying value has been changed.

Question 14

What’s the purpose of us creating type properties?

Answer 14

There will only be one copy of this property, no matter how many instances of that type you create.

So it’s going to always have one value no matter what.