Access Boundaries - Swift Programming

Access control keeps stored details behind public methods and properties.

Hide state behind methods

access_boundaries.swift

struct ScoreBox {
    private var value: Int

    init(start: Int) {
        value = start
    }

    mutating func add(_ amount: Int) {
        value += amount
    }

    var current: Int {
        return value
    }
}

let bonus = 
var box = ScoreBox(start: 10)
box.add(bonus)
let message = "score=\(box.current)"

print(message)

struct ScoreBox {
    private var value: Int

    init(start: Int) {
        value = start
    }

    mutating func add(_ amount: Int) {
        value += amount
    }

    var current: Int {
        return value
    }
}

let bonus = 
var box = ScoreBox(start: 10)
box.add(bonus)
let message = "score=\(box.current)"

print(message)

struct ScoreBox {
    private var value: Int

    init(start: Int) {
        value = start
    }

    mutating func add(_ amount: Int) {
        value += amount
    }

    var current: Int {
        return value
    }
}

let bonus = 
var box = ScoreBox(start: 10)
box.add(bonus)
let message = "score=\(box.current)"

print(message)

access control `private` keeps implementation details inside a type while methods expose the operations callers are allowed to perform.