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iOS Intermediate Swift Properties Type Properties

deepak sharma
deepak sharma
3,844 Points

what does static stand for in this video? please help me to understand

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

struct Map { static let origin = Point()

static var x: Int {
    return origin.x
}

}

1 Answer

krystennant
krystennant
7,197 Points

In this video, he is discussing type properties. These are properties that exist for the TYPE regardless of whether or not there are instances of the method. The definition of 'Static' means 'non moving'. Its not connected to any particular instance.

struct Map {
static let origin = Point(x: 0, y: 0)

// notice how there are no instances of Map created yet 

Map.origin.x // returns 0 
Map.origin.y // returns 0

This property exists even without instances and can be accessed using dot notation from the Type (ie Map.origin)

I have seen these used to denote counts and adding customized ID numbers before, see an example of how changing a type Property can be used:

struct Map {
   static var origin = Point(x: 0, y: 0)
   var instanceOrigin = origin
}

let firstMap = Map()
print(firstMap.instanceOrigin)     // Point(x: 0, y: 0)

// changing the TYPE property 
Map.origin = Point(x:1, y:1) 

let secondMap = Map()

print(firstMap.instanceOrigin)   // Point(x: 0, y: 0) stays the same
print(secondMap.instanceOrigin)   // Point (x: 1, y: 1)   inherits from the type property, which changed

The type property origin is associated with the Struct map - not the instances. Static just means it remains associated with the Type, not particular instances - it doesn't need instances to be accessed.

Hopefully this helps.