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)
    }
}

就像我期望的那样，在我的初始化例程中，

索引设置为[“ E”，“ F”]而不是[“ A”，“ B”]。发生什么事了？

Answer 1

仅在声明时不初始化状态（因为它只初始化一次，然后在视图生命周期内起作用，即在body中起作用）

    @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，这意味着它会获取包装值的输入然后进行修改，因此您永远不要在init中设置@State var，如果您确实想在init中对其进行初始化，则必须直接设置@State var使用@State的init，因为@State是带有@语法糖的结构。更改

 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：初始化未初始化数组

2 个答案: