swiftUi propertWrapper 自定义标记属性
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2024-03-24 12:37:46
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上篇文章我们知道@Status 的作用了
那么我们也可以自己定义类似的这种标签。。
首先我们先来看下不使用属性标签,向导页面如何写
//
// PropertyWrapperView.swift
// learn_swiftUi
//
// Created by liuan on 2020/9/4.
// Copyright © 2020 liuan. All rights reserved.
//
import SwiftUI
extension UserDefaults{
public enum Keys{
static let hadSHowUserGuide = "hadSHowUserGuide"
}
var hasShowUserGuide: Bool{
set{
set(newValue,forKey: Keys.hadSHowUserGuide)
}
get{
bool(forKey: Keys.hadSHowUserGuide)
}
}
}
struct PropertyWrapperView: View {
@State private var showText = UserDefaults.standard.hasShowUserGuide ? "已经展示":"尚未展示"
var body: some View {
Button(action: {
if(!UserDefaults.standard.hasShowUserGuide){
UserDefaults.standard.hasShowUserGuide = true
self.showText = "已经展示"
}
}){
Text(self.showText)
}
}
}
struct PropertyWrapperView_Previews: PreviewProvider {
static var previews: some View {
PropertyWrapperView()
}
}
第一次进来 现实尚未展示 ,点击后现实已经展示
如果改为标签呢
//
// PropertyWrapperView.swift
// learn_swiftUi
//
// Created by liuan on 2020/9/4.
// Copyright © 2020 liuan. All rights reserved.
//
import SwiftUI
//extension UserDefaults{
// public enum Keys{
// static let hadSHowUserGuide = "hadSHowUserGuide"
// }
// var hasShowUserGuide: Bool{
// set{
// set(newValue,forKey: Keys.hadSHowUserGuide)
// }
// get{
// bool(forKey: Keys.hadSHowUserGuide)
// }
// }
//}
@propertyWrapper
struct UserDefaultsWrappler<T> {
var key: String
var defaultValue: T
init(_ key:String, defaultValue: T){
self.key = key
self.defaultValue = defaultValue
}
var wrappedValue: T {
get{
return UserDefaults.standard.value(forKey: key)as? T ?? defaultValue
}
set{
UserDefaults.standard.set(newValue, forKey: key)
}
}}
struct PropertyWrapperView: View {
@UserDefaultsWrappler("hadShowUserGudie", defaultValue: false)
static var hadSHownUserGudie: Bool
@State private var showText = PropertyWrapperView.hadSHownUserGudie ? "已经展示":"尚未展示"
var body: some View {
Button(action: {
if( !PropertyWrapperView.hadSHownUserGudie){
PropertyWrapperView.hadSHownUserGudie = true
self.showText = "已经展示"
}
}){
Text(self.showText)
}
}
}
struct PropertyWrapperView_Previews: PreviewProvider {
static var previews: some View {
PropertyWrapperView()
}
}