Swift Protocol-Oriented Programming by Jon Hoffman

Author:Jon Hoffman
Language: eng
Format: epub, pdf
Tags: COM051460 - COMPUTERS / Programming / Mobile Devices, COM051000 - COMPUTERS / Programming / General, COM000000 - COMPUTERS / General
Publisher: Packt Publishing
Published: 2019-06-28T14:51:44+00:00

If we run this code, we will see the following output, which illustrates how ARC works:

Initializing class with name One

Initializing class with name Two

Setting class1ref1 to nil

Releaseing class with name One

Setting class2ref1 to nil

Setting class2ref2 to nil

Releaseing class with name Two

From the example, it seems that ARC handles memory management pretty well. However, it is possible to write code that will prevent ARC from working properly.

Strong reference cycles

A strong reference cycle is where the instances of two classes hold a strong reference to each other, preventing ARC from releasing either instance. Once again, we are not able to use a Playground for this example, so we need to create an Xcode project. In this project, we start off by creating two classes named MyClass1_Strong and MyClass2_Strong with the following code:

class MyClass1_Strong {

var name = ""

var class2: MyClass2_Strong?

init(name: String) {

self.name = name

print("Initializing class1_Strong with name \(self.name)")

}

deinit {

print("Releasing class1_Strong with name \(self.name)")

}

}

class MyClass2_Strong {

var name = ""

var class1: MyClass1_Strong?

init(name: String) {

self.name = name

print("Initializing class2_Strong with name \(self.name)")

}

deinit {

print("Releasing class2_Strong with name \(self.name)")

}

}

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