https://github.com/p-x9/associatedobject

🔗 Swift Macro for allowing variable declarations even in class extensions
https://github.com/p-x9/associatedobject

macros swiftmacros swiftpackage swiftpackagemanager

Last synced: 9 months ago
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🔗 Swift Macro for allowing variable declarations even in class extensions

• Host: GitHub
• URL: https://github.com/p-x9/associatedobject
• Owner: p-x9
• License: mit
• Created: 2023-06-12T02:12:30.000Z (over 2 years ago)
• Default Branch: main
• Last Pushed: 2024-11-28T09:31:07.000Z (about 1 year ago)
• Last Synced: 2025-03-29T15:08:20.302Z (9 months ago)
• Topics: macros, swiftmacros, swiftpackage, swiftpackagemanager
• Language: Swift
• Homepage:
• Size: 294 KB
• Stars: 134
• Watchers: 1
• Forks: 4
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# AssociatedObject

Swift Macro for allowing variable declarations even in class extensions.

It is implemented by wrapping `objc_getAssociatedObject`/`objc_setAssociatedObject`.

[![Github issues](https://img.shields.io/github/issues/p-x9/AssociatedObject)](https://github.com/p-x9/AssociatedObject/issues)

[![Github forks](https://img.shields.io/github/forks/p-x9/AssociatedObject)](https://github.com/p-x9/AssociatedObject/network/members)

[![Github stars](https://img.shields.io/github/stars/p-x9/AssociatedObject)](https://github.com/p-x9/AssociatedObject/stargazers)

[![Github top language](https://img.shields.io/github/languages/top/p-x9/AssociatedObject)](https://github.com/p-x9/AssociatedObject/)

## Installation

#### SPM

```swift

.package(url: "https://github.com/p-x9/AssociatedObject", from: "0.10.3")

```

#### CocoaPods

Add below to your `Podfile`.

```

pod 'AssociatedObject', git: 'https://github.com/p-x9/AssociatedObject', tag: '0.10.3'

```

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.

![Alt text](image.png)

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

```swift

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

```swift

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.

```swift

@AssociatedObject(.copy(nonatomic))

public var hello: String = "こんにちは" {

    didSet {

        print("didSet")

    }

    willSet {

        print("willSet: \(newValue)")

    }

}

// ↓↓↓ expand to ... ↓↓↓

public var hello: String = "こんにちは" {

    get {

        objc_getAssociatedObject(

            self,

            &Self.__associated_helloKey

        ) as? String

        ?? "こんにちは"

    }

    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](./LICENSE)