🚥State

SwiftUI ⟩ Data Flow ⟩ State

注意：@State 與 @Binding 只用於 value type❗

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• init State

• Binding State

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State 變數可以用 initializer 初始化 👉 範例： Swatch

問：Can we change a State var in ViewBuilder❓

答：

• ... SwiftUI is a recipe, it's not an event system. You don't change state variables in the body function, you set up how things should react when state variables change externally. 👉 StackOverflow

State is a value, or a set of values, that can change over time, and that affects a view’s behavior, content, or layout.

In SwiftUI, a property that’s marked with @State (or @Binding), isn’t just one property. It’s three properties! 👉 The Inner Workings of State Properties of SwiftUI - Medium

對每一個 @State var state: T 變數來說，它的內部都隱含了「三個變數」：

• _state: State<T> 就是 @State 變數本身，初始化時用到的初始值 (initial value) 會放在 _state.wrappedValue 裡面。

• $state: Binding<T> 它會回傳 _state.projectedValue，用來做「雙向連結」用的。

• state: T 這是一個 computed property，用來回傳或設定 _state.wrappedValue。

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• 💈 動態底線

• ✨ Swatch - initialze State var, report view preference.

struct LandmarkList: View {
    
    /// ⭐️ state is always private
    @State private var showFavoritesOnly = true
    
    var body: some View { ... }
}

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• SwiftUI Tutorials ⟩ Handling User Input ⟩ Sec. 2: Filter the List View

• SwiftUI ⟩ State and Data Flow

  • State (struct)

• SwiftOnTap ⟩ State

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• The Inner Workings of State Properties of SwiftUI

• CodeWithChris ⟩ SwiftUI State Properties (Lesson 11 of 14)

• Sarun > @State variable initialization in SwiftUI

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• is Property Wrappers.

• Binding can be created from.

• Swatch shows how to initialize a State variable in an initializer.

• mutating getter / nonmutating setter - ?

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• SwiftUI @State var initialization issue - how to init a State var?

• Why no setting of intial state?

• Change @State in a @ViewBuilder closure ⭐️

• A @State static property is being reinitiated without notice ⭐️ don't use a @State static private var ❓