👷‍♀️ Closure-based delegation without memory leaks
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README.md

README.md

Delegated

Swift Platform

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

Delegated is available through Carthage. To install, just write into your Cartfile:

github "dreymonde/Delegated" ~> 0.1.0

Delegated is also available through Cocoapods:

pod 'Delegated', '~> 0.1.0'

And Swift Package Manager:

dependencies: [
    .Package(url: "https://github.com/dreymonde/Delegated.git", majorVersion: 0, minor: 1),
]

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

See also