SwiftUI視圖：兩個不同的初始化程式：無法將“文本”型別的值轉換為閉包結果型別“內容”

代碼：

import SwiftUI

public struct Snackbar<Content>: View where Content: View {
    private var content: Content

// Works OK
    public init(@ViewBuilder content: () -> Content) {
        self.content = content()
    }

    init(_ text: String) {
        self.init {
            Text(text) // cannot convert value of type 'Text' to closure result type 'Content'
                .font(.subheadline)
                .foregroundColor(.white)
                .multilineTextAlignment(.leading)
        }
    }

    public var body: some View {
        HStack {
            VStack(alignment: .leading, spacing: 4) {
                content
            }
            Spacer()
        }
        .frame(maxWidth: .infinity,
               minHeight: 26)
        .padding(.fullPadding)
        .background(Color.black)
        .clipShape(RoundedRectangle(cornerRadius: .defaultCornerRadius))
        .shadow(color: Color.black.opacity(0.125), radius: 4, y: 4)
        .padding()
    }
}

我收到此錯誤：

無法將“文本”型別的值轉換為閉包結果型別“內容”

我想要實作的目標是擁有 2 個單獨的初始化程式，一個用于 type 的內容，View另一個是字串的快捷方式，它將放置一個Text具有某種樣式的預定義組件來代替Content.

Text如果是，為什么我會收到此錯誤some View并且我認為它應該編譯。

uj5u.com熱心網友回復：

一種方法是使內容可選并使用另一個文本變數并基于 nil 值顯示視圖。

public struct Snackbar<Content>: View where Content: View {
    private var content: Content? // <= Here
    private var text: String = "" // <= Here
    
    // Works OK
    public init(@ViewBuilder content: () -> Content) {
        self.content = content()
    }
    
    init(_ text: String) {
        self.text = text // <= Here
    }
    
    public var body: some View {
        HStack {
            VStack(alignment: .leading, spacing: 4) {
                if let content = content { // <= Here
                    content
                } else {
                    Text(text)
                        .font(.subheadline)
                        .foregroundColor(.white)
                        .multilineTextAlignment(.leading)
                }
            }
            Spacer()
        }
        // Other code

你也可以使用AnyView

public struct Snackbar: View {
    private var content: AnyView // Here
    
    // Works OK
    public init<Content: View>(@ViewBuilder content: () -> Content) {
        self.content = AnyView(content()) // Here
    }
    
    init(_ text: String) {
        self.content = AnyView(Text(text)
                            .font(.subheadline)
                            .foregroundColor(.white)
                            .multilineTextAlignment(.leading)
        ) // Here
    }
    
    public var body: some View {
        HStack {
            VStack(alignment: .leading, spacing: 4) {
                self.content
            }
            Spacer()
        }

uj5u.com熱心網友回復：

您可以指定Content.

代碼：

public struct Snackbar<Content>: View where Content: View {
    private var content: Content

// Works OK
    public init(@ViewBuilder content: () -> Content) {
        self.content = content()
    }

    init(_ text: String) where Content == ModifiedContent<Text, _EnvironmentKeyWritingModifier<TextAlignment>> {
        self.init {
            Text(text)
                .font(.subheadline)
                .foregroundColor(.white)
                .multilineTextAlignment(.leading) as! ModifiedContent<Text, _EnvironmentKeyWritingModifier<TextAlignment>>
        }
    }

    /* ... */
}

這里唯一的區別是 .where之后init和強制轉換為init.

為避免特定型別，您可以將其抽象為單獨的視圖：

init(_ text: String) where Content == ModifiedText {
    self.init {
        ModifiedText(text: text)
    }
}

/* ... */

struct ModifiedText: View {
    let text: String

    var body: some View {
        Text(text)
            .font(.subheadline)
            .foregroundColor(.white)
            .multilineTextAlignment(.leading)
    }
}

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