SwiftUI：初始化不初始化数组

Question

我在初始化数组时遇到问题：

struct ProjectList: View
{
    @ObservedObject var store: ProjectStore
    @Binding var searchText: String

    @State private var query: [Project] = []
    @State private var indexes: [String] = ["E","F"]
     
    init(store: ProjectStore, searchText: Binding<String>)
    {
        self.store = store
        self._searchText = searchText
        self.query = []
        self.indexes = ["C","D"]
        indexes = ["A","B"] //store.getIndexes(search: searchText.wrappedValue)
        print (indexes)
    }
}

indexes 在我的 init 例程中被设置为 ["E","F"] 而不是我所期望的 ["A","B"]。发生了什么事？

Answer 1

声明时不要初始化状态（因为它只初始化一次然后在视图生命周期内工作，即在body）

    @State private var indexes: [String]        // << only declare

    init(store: ProjectStore, searchText: Binding<String>)
    {
        ...
        self._indexes = State(initialValue: ["C","D"])  // initialise !!

Answer 2

@State 是属性包装器，这意味着它接受包装值的输入然后修改它，你不应该在 init 中设置 @State var，如果你真的想要，你必须直接设置 @State var在 init 中初始化它，你必须使用 @State 的 init，因为 @State 是一个带有 @ 语法糖的结构。变化

 init(store: ProjectStore, searchText: Binding<String>)
    {
        self.store = store
        self._searchText = searchText
        self.query = []
        self.indexes = ["C","D"]
        indexes = ["A","B"] //store.getIndexes(search: searchText.wrappedValue)
        print (indexes)
    }

至：

 init(store: ProjectStore, searchText: Binding<String>)
    {
        self.store = store
        self._searchText = searchText
        self.query = []
        self.indexes = ["C","D"]
        indexes =  State(initialValue: ["C","D"]) //changed value
        print (indexes)
    }

SwiftUI：初始化不初始化数组

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