Как Swift работает с памятью: подробный гайд для разработчиков. Часть 2

Задачи

Задача 1

class ClassA {
     var next: ClassB? = nil


}
class ClassB {
     var next: ClassA? = nil
}
let a = ClassA()
 let b = ClassB()
 a.next = b
 b.next = a

class ClassA {
     var next: ClassB? = nil


}
class ClassB {
     weak var next: ClassA? = nil


}


let a = ClassA()
 let b = ClassB()
 a.next = b
 b.next = a

Задача 2

class MyClass {}
 weak var array = [MyClass()]

class MyClass {}
 class WeakBox {


    weak var myClass: MyClass?


    init(_ myClass: MyClass) {
         self.myClass = myClass


} }
var array = [WeakBox(MyClass())]

Задача 3

@_optimize(none)
 func foo(_ number: Int) {


    guard number != 0 else { return }
     let newNumber = number - 2
     foo(newNumber)
} 
foo(3)

@_optimize(none)
 func foo(_ number: Int) {


    guard number != 0 else { return }
     let newNumber = number - 2
     foo(newNumber)
} 
foo(3)

Задача 4

struct MyStruct {
     var next: MyStruct?


}

class MyClass {
     var next: MyClass?
}

enum MyEnum {
     case next(MyEnum)
}

struct MyStruct {
     var next: MyStruct?
}

class MyClass {
     var next: MyClass?

}

indirect enum MyEnum {
     case next(MyEnum)

}

Задача 5

struct StructA {
     let a: Bool = false
     let b: UInt64 = 0


}
 print("Size: \(MemoryLayout<StructA>.size); Stride:
 \(MemoryLayout<StructA>.stride)")


struct StructB {
     let a: UInt64 = 0
     let b: Bool = false


}
 print("Size: \(MemoryLayout<StructB>.size); Stride:
 \(MemoryLayout<StructB>.stride)")


class MyClass {
     let a: UInt64 = 0
     let b: Bool = false


}
 print("Size: \(MemoryLayout<MyClass>.size); Stride:
 \(MemoryLayout<MyClass>.stride)")

struct StructA {
     let a: Bool = false
     let b: UInt64 = 0


}

struct StructB {
     let a: UInt64 = 0
     let b: Bool = false


}

Задача 6

protocol MyProtocol {
     var a: UInt64 { get }


}
 struct StructA: MyProtocol {


  
    let a: UInt64 = 1
 }


struct StructB: MyProtocol {
     let a: UInt64 = 10
     let b: UInt64 = 20


}
let a = StructA()
 let b = StructB()
 let array: [MyProtocol] = [a, b]


print(MemoryLayout.size(ofValue: a))
 print(MemoryLayout.size(ofValue: b))
 print(MemoryLayout.size(ofValue: array[0]))
 print(MemoryLayout.size(ofValue: array[1]))

Задача 7

protocol ProtocolA {}
 protocol ProtocolB: AnyObject {}


class MyClass: ProtocolA, ProtocolB {}


let a: ProtocolA = MyClass()
 let b: ProtocolB = MyClass()
 let c: ProtocolA & ProtocolB = MyClass()


print(MemoryLayout.size(ofValue: a))
 print(MemoryLayout.size(ofValue: b))
 print(MemoryLayout.size(ofValue: c))

Задача 8

protocol ProtocolA {
     var b: ProtocolB? { get set }


}
protocol ProtocolB {
     var a: ProtocolA? { get set }


}
 struct StructA: ProtocolA {


    var b: ProtocolB?


// Поля в 4 машинных слова,
// чтобы превысить размер полей под данные в экзистенциальном контейнере и структура оказалась на куче
    let int1: Int = 1
     let int2: Int = 2
     let int3: Int = 3
     let int4: Int = 4


}
 struct StructB: ProtocolB {


    var a: ProtocolA?


// Поля в 4 машинных слова,
// чтобы превысить размер полей под данных в экзистенциальном контейнере и структура оказалась на куче
    let int1: Int = 1
     let int2: Int = 2
     let int3: Int = 3
     let int4: Int = 4


}
var a: ProtocolA = StructA()
 var b: ProtocolB = StructB()
 a.b = b
 b.a = a

Задача 9

class MyClass {
     var value: Int = 0


}
 var myClass = MyClass()


myClass.value = 1


let printValue = { // Если добавить `[myClass] in`, изменится ли что-то? print(myClass.value)
}
 printValue()


myClass = MyClass()
 myClass.value = 2
 printValue()

Задача 10

import Foundation
 class MyClass {


    private var callback: (() -> ())?


    func foo() {
         callback = {


            DispatchQueue.main.async { [weak self] in
                 self?.updateView()


} }
}
    private func updateView() {
         // ...
} }
let myClass = MyClass()
 myClass.foo()

import Foundation
 class MyClass {


    private var callback: (() -> ())?


    func foo() {
         callback = { [weak self] in


            DispatchQueue.main.async {
                 self?.updateView()


} }
}
    private func updateView() {
         // ...


} }
let myClass = MyClass()
 myClass.foo()

Задача 11

class MyClass {
     var closure: (() -> ())?


    init(closure: (() -> Void)? = nil) {
         self.closure = closure ?? foo


}
    private func foo() {
         // ...


} }

class MyClass {
     var closure: (() -> ())?


    init(closure: (() -> Void)? = nil) {
         self.closure = closure ?? { [weak self] in self?.foo() }


}
    private func foo() {
         // ...


} }

Задача 12

class MyView {
     var subviews: [MyView] = []


    deinit {
         print("Deinit \(Self.self)")


} }
class MyLabelView: MyView {
     func update(text: String) {


        print("Update text to \(text)")
     }


}
 class MyViewController {


    private var view: MyView?
     private var updateText: ((String) -> ())?


    func loadView() {
         self.view = MyView()
         let labelView = MyLabelView()
         view?.subviews.append(labelView)


        updateText = { [unowned labelView] in
             labelView.update(text: $0)


} }
    func update(text: String) {
         guard view != nil else { return }
         updateText?(text)
}
    func cleanView() {
         view = nil


} }
let vc = MyViewController()
 vc.loadView()
 vc.update(text: "Hello!")
 vc.cleanView()
 vc.update(text: "Bye!")

class MyView {
     var subviews: [MyView] = []


    deinit {
         print("Deinit \(Self.self)")


} }
class MyLabelView: MyView {
     
    func update(text: String) {
         print("Update text to \(text)")


} }
class MyViewController {
     private var view: MyView?


    private var labelView: MyLabelView?


    func loadView() {
         self.view = MyView()
         let labelView = MyLabelView()
         self.labelView = labelView
         view?.subviews.append(labelView)
}
    func update(text: String) {
         labelView?.update(text: text)


}
    func cleanView() {
         view = nil


        labelView = nil
     }


}
let vc = MyViewController()
 vc.loadView()
 vc.update(text: "Hello!")
 vc.cleanView()
 vc.update(text: "Bye!").

Задача 13

class ClassA {
     var b = ClassB(a: self)


    func foo() {
         print(b)


} }
class ClassB {
     let a: ClassA


    init(a: ClassA) {
self.a = a }
}
let a = ClassA()
 a.foo()

class ClassALazy {
     lazy var b = ClassBLazy(a: self)


    func foo() {
         print(b)


} }
class ClassBLazy {
     weak var a: ClassALazy?


    init(a: ClassALazy) {
         self.a = a


} }
let aLazy = ClassALazy()
 aLazy.foo()

class ClassAOpt {
     var b: ClassBOpt?


    init() {
         self.b = ClassBOpt(a: self)


}
    func foo() {
         guard let b else { return }
         print(b)


} }
class ClassBOpt {
     weak var a: ClassAOpt?


    init(a: ClassAOpt) {
         self.a = a


} }
let aOpt = ClassAOpt()
 aOpt.foo()

Задача 14

class MyClass {


    static let shared = MyClass()


    init() {
         print("Init \(Self.self)")


}
    func foo() {
         // ...


} }
let myClass = MyClass()
 print("Hello")
 MyClass.shared.foo()

Init MyClass
  Hello
  Init MyClass

Задача 15

struct MyStruct {
     var a = 1
     var b = 2


}
class MyClass {
     static var myStruct = MyStruct()


}
func swap(_ a: inout Int, _ b: inout Int) {
     let buff = a


a=b
b = buff 
}
swap(&MyClass.myStruct.a, &MyClass.myStruct.b) 

Итоги