Clamping.swift

    @propertyWrapper
    struct Clamping<Value: Comparable> {
        var value: Value
        let range: ClosedRange<Value>
    
        init(wrappedValue value: Value, _ range: ClosedRange<Value>) {
            precondition(range.contains(value))
            self.value = value
            self.range = range
        }
    
        var wrappedValue: Value {
            get { value }
            set { value = min(max(range.lowerBound, newValue), range.upperBound) }
        }
    }
    // 使用:
    @Clamping(wrappedValue: 1.0, 0...14) var pH: Double