实现封装 SwiftUI Picker 控件，达到通过构造不同类型的数据，就能渲染对应类型的 Picker。(The SwiftUI Picker control is encapsulated, so that by constructing different types of data, the corresponding type of Picker can be rendered.)

Step1 Picker data structrure

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class IdentifiableString: Identifiable {
    
    internal init(s: String) {
        self.str = s
        self.id = s
    }
    
    let str: String
    var id: String
}

open class MPickerData<Content> {
    
    public init(title: String, key: String, values: [Content]) {
        self.title = title
        self.key = key
        self.values = values
        self.select = KV.shared.get(key: key)
    }
    
    let title: String
    let key: String
    let values: [Content]
    var select: Content?
    
    var idValues: [IdentifiableString] {
        values.map { item in
            IdentifiableString(s: "\(item)")
        }
    }
    
    open func binding() -> Binding<String>? {
        return nil
    }
    
    func updateSelect(_ newValue: Content) {
        self.select = newValue
        KV.shared.set(key: self.key, value: newValue)
    }
}

KV: UserDefaults wraper class

Step2 Implement for some types

Int Picker

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public class MIntPicker: MPickerData<Int> {
    
    public override func binding() -> Binding<String> {
        let binding = Binding<String> {
            return "\(self.select ?? KV.shared.get(key: self.key) ?? 0)"
        } set: { newValue in
            if let nInt = Int(newValue) {
                self.updateSelect(nInt)
            }
        }
        return binding
    }
}

String Picker

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public class MStringPicker: MPickerData<String> {
    
    public override func binding() -> Binding<String> {
        let binding = Binding<String> {
            return self.select ?? KV.shared.get(key: self.key) ?? ""
        } set: { newValue in
            self.updateSelect(newValue)
        }
        return binding
    }
}

Step3 Implement Picker View

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import SwiftUI

struct MPickerView<Content>: View {
    
    @State var pickerData: MPickerData<Content>
    
    var body: some View {
        VStack {
            Text(pickerData.title).font(.title)
            if let binding = pickerData.binding() {
                Picker(pickerData.title, selection: binding) {
                    ForEach(pickerData.idValues) { idV in
                        Text(idV.str)
                    }
                }.pickerStyle(WheelPickerStyle())
            }
        }
    }
}

Usage

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let pickers = [
	MIntPicker(title: "Select Int", key: "key_int", values: [1, 2, 3, 4]),
	MFloatPicker(title: "Select Float", key: "key_float", values: [1.0, 2.4, 3.5, 4.6]),
	MDoublePicker(title: "Select Double", key: "key_double", values: [1.1, 2.2, 3.3333, 4.56]),
	MStringPicker(title: "Select String", key: "key_string", values: ["aaa", "bbb", "ccc", "ddd"])
]

let pickerView = MPickerView(pickerData: pickers)

SwiftUI Picker Implementation

Step1 Picker data structrure

Step2 Implement for some types

Int Picker

String Picker

Step3 Implement Picker View

Usage

See Also