chenhaiteng/SwiftClamping

Swift-Clamping

Purpose:

1. For values that have upper and lower bound, provide a way to not write duplicate code.
2. In swift, when one try to preprocess an property before apply it, it needs following code:

    private var _computedVarStorage: Int
    public var computedVar: Int {
        get {
            return _computedVarStorage
        }
        set {
            _computedVarStorage = newValue*10
        }
    }

Because the get/set syntax will change variable to computed variable, it always need write a getter, even through we want a write-only property.

Also, to keep the modified value, a extra storage variable is needed, and it looks ugly.

3. In additionally, we also want the solution could be apply to protocol.

Solution:

1. Use @propertyWrapper to apply clamp; replace max, min and degree into one declaration.

    @Clamping(max: 0.0, min: 360.0) var degree = 0.0
    @Clamping(0.0...1.0) var value = 0.5

2. In some situation, it need modify the range later, property wrapper use projectedValue to implement this requirement:

    @Clamping(0.0...1.0) var value = 0.5
    $value = 0.0...10.0

3. Although @propertyWrapper is useful, it hard to apply this mechanism to protocol. However, there has a workaround:

protocol ClampProtocol {
    var degree: Double // Can declare as @Clamping
    var range: ClosedRange<Double> // Can map to projectedValue in @Clamping
}

struct ClampStruct {
    @Clamping(0.0...360.0) var degree = 0.0
    var range: ClosedRange<Double> {
        get { $degree }
        set { $degree = newValue }
    }
}

With this workaround, all class/struct implement ClampProtocol can apply @Clamping to simplify the effort to write clamp function, and keep it interface clear.

The detail about the implementation of @Clamping could be refer to : Clamping.swift

Installation:

CocoaPods

SwiftClamping is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'SwiftClamping'

Swift Package Manager

- Add to Xcode

1. File > Swift Packages > Add Package Dependency...
2. Choose Project you want to add SwiftClamping
3. Paste repository https://github.com/chenhaiteng/SwiftClamping.git
4. Rules > Version: Up to Next Major 1.0.1 It's can also apply Rules > Branch : Main to access latest code.

Note: It might need to link SwiftClamping to your target maunally.

1. Open Project Editor by tap on root of project navigator
2. Choose the target you want to use SwiftClamping.
3. Choose Build Phases, and expand Link Binary With Libraries
4. Tap on + button, and choose SwiftClamping to add it.

- Add to SPM package

dependencies: [
    .package(url: "https://github.com/chenhaiteng/SwiftClamping.git", from: "1.0.1")
],
targets: [
    .target(
        name: "MyPackage",
        dependencies: ["SwiftClamping"]),
]

References:

Property Wrapper - Swift Doc

Property Wrapper(SE-0258) - Swift Evolution

Swift: Why does a variable with a setter must also have a getter? - stackoverflow

PropertyWrappers and protocol declaration? - stackoverflow

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