Delegated

👷‍♀️ Closure-based delegation without memory leaks

Programming language: Swift

License: MIT License

Tags: Utility    

Latest version: v0.1.2

README

Delegated

Delegated is a super small package that solves the retain cycle problem when dealing with closure-based delegation.

Medium post here.

Usage

Before:

self.downloader = ImageDownloader()
downloader.didDownload = { [weak self] image in
    guard let strongSelf = self else {
        return
    }
    strongSelf.currentImage = image
}

After:

self.downloader = ImageDownloader()
downloader.didDownload.delegate(to: self) { (self, image) in
    self.currentImage = image
}

No retain cycles! No memory leaks! No [weak self]! 🎉

Guide

Creating a delegated function

class NumberPrinter {
    var numberToString = Delegated<Int, String>()
}

Registering as a delegate

// somewhere inside init() or viewDidLoad() or similar
self.printer = NumberPrinter()
printer.numberToString.delegate(to: self) { (self, number) -> String in
    return self.convert(number: number)
}

By default, delegate(to:with:) will wrap self in a weak reference so that you don't need to remember to write [weak self] every time. This is the main feature of Delegated, but if this is not the behavior you want, you can use stronglyDelegated(to:with:) or manuallyDelegated(with:):

self.printer = NumberPrinter()
printer.numberToString.stronglyDelegate(to: self) { (self, number) -> String in
    // will hold a strong reference to  `self`
    return self.convert(number: number) 
}

let printer = NumberPrinter()
printer.numberToString.manuallyDelegate(with: { number in
    return String(number)
})

Calling a delegate

class NumberPrinter {

    var numberToString = Delegated<Int, String>()

    func printNumber(_ number: Int) {
        // .call returns nil if no delegate was set
        guard let string = numberToString.call(number) else {
            return
        }
        print(string)
    }

}

Removing a delegate

var numberToString = Delegated<Int, String>()
// ...
numberToString.removeDelegate()

Checking if delegate is set

var numberToString = Delegated<Int, String>()
// ...
numberToString.isDelegateSet // Bool

Installation

Swift Package Manager

Starting with Xcode 11, Delegated is officially available only via Swift Package Manager.

In Xcode 11 or grater, in you project, select: File > Swift Packages > Add Pacakage Dependency

In the search bar type

https://github.com/dreymonde/Delegated

and when you find the package, with the next button you can proceed with the installation.

If you can't find anything in the panel of the Swift Packages you probably haven't added yet your github account. You can do that under the Preferences panel of your Xcode, in the Accounts section.

For command-line based apps, you can just add this directly to your Package.swift file:

dependencies: [
    .package(url: "https://github.com/dreymonde/Delegated", from: "0.1.2"),
]

Manual

Of course, you always have an option of just copying-and-pasting the code - Delegated is just one file, so feel free.

Deprecated dependency managers

Last Delegated version to support Carthage and Cocoapods is 0.1.1. Carthage and Cocoapods will no longer be officially supported.

Carthage:

github "dreymonde/Delegated" ~> 0.1.1

Cocoapods:

pod 'Delegated', '~> 0.1.1'

See also

• krzysztofzablocki/Strongify - a 1-file µframework providing a nicer API for avoiding weak-strong dance.