Introduction to Swift

Apr 24 2024 · Swift 5.10, iOS 17, Xcode 15

Lesson 03: Classes & Structures

Memory Demo

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You’ve learned about initializers and the init function, which prepares the objects inside a struct or a class with their initial values. In this demo, you’ll learn about the deinit function for reference types which is responsible for the de-initialization of the object and cleaning it up when it’s being cleaned from memory. Only classes have a deinit; structs do not. Later in the demo, you’ll learn about the different sizes of data types and how much memory they allocate when you create instances from them.

class ExampleClass {

}

init() {
  print("Instance Created")
}

deinit {
  print("Instance Deleted")
}

do {
  print("Start Scope - 1")
}
print("End Scope - 1")

var variable1 = ExampleClass()

func getInstance() -> ExampleClass {
  print("getInstance() called")
  return ExampleClass()
}

do {
  print("Start Scope - 2")
  var variable1 = getInstance()
  print("Function call finished")
}
print("End Scope - 2")

do {
  print("Start Scope - 3")
  var variable1 = ExampleClass()
  do {
    print("Start Scope - 3 : Inner Scope - 1 \(variable1)")
    variable1 = ExampleClass()
  }
  print("End Scope - 3 : Inner Scope - 1")
}
print("End Scope - 3")

let boolValue = false
MemoryLayout.size(ofValue: boolValue)

let intValue: Int = 10
MemoryLayout.size(ofValue: intValue)

let floatValue: Float = 10
MemoryLayout.size(ofValue: floatValue)

let doubleValue: Double = 10
MemoryLayout.size(ofValue: doubleValue)

let int8Value: Int8 = 10
MemoryLayout.size(ofValue: int8Value)

let int16Value: Int16 = 10
MemoryLayout.size(ofValue: int16Value)

let int32Value: Int32 = 10
MemoryLayout.size(ofValue: int32Value)

let int64Value: Int64 = 10
MemoryLayout.size(ofValue: int64Value)

struct TwoIntsStruct {
  var intValue1: Int = 0
  var intValue2: Int = 0
}

struct FourIntsStruct {
  var intValue1: Int = 0
  var intValue2: Int = 0
  var intValue3: Int = 0
  var intValue4: Int = 0
}

MemoryLayout.size(ofValue: TwoIntsStruct())
MemoryLayout.size(ofValue: FourIntsStruct())

struct EmptyStruct {}

MemoryLayout.size(ofValue: EmptyStruct())

class TwoIntsClass {
  var intValue1: Int = 0
  var intValue2: Int = 0
}

class FourIntsClass {
  var intValue1: Int = 0
  var intValue2: Int = 0
  var intValue3: Int = 0
  var intValue4: Int = 0
}

MemoryLayout.size(ofValue: TwoIntsClass())
MemoryLayout.size(ofValue: FourIntsClass())

class EmptyClass {}
MemoryLayout.size(ofValue: EmptyClass())
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