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
self?.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 // BoolInstallation
Delegated is available through Carthage. To install, just write into your Cartfile:
github "dreymonde/Delegated" ~> 0.1.0Delegated 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
- krzysztofzablocki/Strongify - a 1-file µframework providing a nicer API for avoiding weak-strong dance.
