AssociatedObject
Swift Macro for allowing variable declarations even in class extensions.
It is implemented by wrapping objc_getAssociatedObject/objc_setAssociatedObject.
Installation
SPM
.package(url: "https://github.com/p-x9/AssociatedObject", from: "0.8.0")CocoaPods
Add below to your Podfile.
pod 'AssociatedObject', git: 'https://github.com/p-x9/AssociatedObject', tag: '0.8.0'
After pod install, you can use this Macro in your project.
Additionally, if you encounter build error like Expansion of macro 'AssociatedObject' did not produce a non-observing accessor. You should check your project setting Build Settings-OTHER_SWIFT_FLAGS.
There should be additional flags like so.
If not, you can add these two lines by yourself.
-load-plugin-executable
${PODS_ROOT}/AssociatedObject/Binary/AssociatedObjectPlugin#AssociatedObjectPlugin
Usage
For example, you can add a new stored property to UIViewController by declaring the following
import AssociatedObject
extension UIViewController {
@AssociatedObject(.retain(nonatomic))
var text = "text"
/* OR */
@AssociatedObject(.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
var text = "text"
static var customKey = ""
@AssociatedObject(.OBJC_ASSOCIATION_RETAIN_NONATOMIC, key: customKey)
var somevar = "text"
}Declared properties can be used as follows
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
print(text) // => "text"
text = "hello"
print(text) // => "hello"
}
}willSet/didSet
Properties defined using @AssociatedObject can implement willSet and didSet.
In swift, it is not possible to implement willSet and didSet at the same time as setter, so they are expanded as follows.
@AssociatedObject(.copy(nonatomic))
public var hello: String = "ใใใซใกใฏ" {
didSet {
print("didSet")
}
willSet {
print("willSet: \(newValue)")
}
}
// โโโ expand to ... โโโ
public var hello: String = "ใใใซใกใฏ" {
get {
objc_getAssociatedObject(
self,
&Self.__associated_helloKey
) as? String
?? "ใใใซใกใฏ"
}
set {
let willSet: (String) -> Void = { [self] newValue in
print("willSet: \(newValue)")
}
willSet(newValue)
let oldValue = hello
objc_setAssociatedObject(
self,
&Self.__associated_helloKey,
newValue,
.copy(nonatomic)
)
let didSet: (String) -> Void = { [self] oldValue in
print("didSet")
}
didSet(oldValue)
}
}License
AssociatedObject is released under the MIT License. See LICENSE