赋值MyScruct().var = results不会导致赋值

Question

好的..。可能是不好的标题。但在这里，问题来了。

struct DeckView: View {
    
    @State public var results = [ScryfallCard]()
    
    var body: some View {
        List(results, id: \.id ) { item in
            
            Mkae a list containing the results. 
            
        }.onAppear {
            ScryfallData().parseBulkData()
            print("Type of results::", type(of: results))
            print("results.capacity:", results.capacity)
        }
    }
}

struct ScryfallData {

    func parseBulkData() {
        let fm = FileManager.default
        let path = Bundle.main.resourcePath
        let items = try! fm.contentsOfDirectory(atPath: path!)
        var oracleFileName = ""
        
        for fileName in items {
            if fileName .hasPrefix("oracle-cards"){
                oracleFileName = fileName
            }
        }
        
        print("if let savedJson = Bundle.main.url")
        if let savedJson = Bundle.main.url(forResource: oracleFileName, withExtension: "") {
            if let dataOfJson = try? Data(contentsOf: savedJson) {
                print("if let dataOfJSON: \(dataOfJson)")
                do {
                    let scryfallDecodeData = try JSONDecoder().decode([ScryfallCard].self, from: dataOfJson)
                    print("scryfallDecodeData.capacity:", scryfallDecodeData.capacity)
                    
/* error here*/         DeckView().results = scryfallDecodeData
                    
                    print("DeckView().results: ", DeckView().results)
                    print("Decoded data:", type(of: scryfallDecodeData))
                } catch {
                    debugPrint("decode failed")
                }
            }
        }
    }
}

我一直在调试器里看到一个空白列表...

if let dataOfJSON: 73545913 bytes
scryfallDecodeData.capacity: 24391
DeckView().results:  []
Decoded data: Array<ScryfallCard>
Type of results:: Array<ScryfallCard>
results.capacity: 0

这意味着在这里标记为错误的行上，我将解码的数据赋值给DeckView().results变量，但最终结果是数据没有被赋值。知道我做错了什么吗？

Answer 1

您不应该从视图模型(ScryfallData)创建View，而应该从parseBulkData函数返回解码的数据，并将其分配给View的onAppear中的results。

你的模型永远不应该知道你的UI。你的UI (在SwiftUI的情况下是View)应该拥有模型，而不是反过来。这实现了良好的关注点分离，并使您的业务逻辑平台和UI不可知。

struct DeckView: View {

    @State public var results = [ScryfallCard]()

    var body: some View {
        List(results, id: \.id ) { item in
            Text(item.text)
        }.onAppear {
            self.results = ScryfallData().parseBulkData()
        }
    }
}

struct ScryfallData {
    func parseBulkData() -> [ScryfallCard] {
        let fm = FileManager.default
        let path = Bundle.main.resourcePath
        let items = try! fm.contentsOfDirectory(atPath: path!)
        var oracleFileName = ""

        for fileName in items {
            if fileName .hasPrefix("oracle-cards"){
                oracleFileName = fileName
            }
        }

        if let savedJson = Bundle.main.url(forResource: oracleFileName, withExtension: "") {
            do {
                let jsonData = try Data(contentsOf: savedJson)
                let scryfallDecodeData = try JSONDecoder().decode([ScryfallCard].self, from: jsonData)
                return scryfallDecodeData
            } catch {
                debugPrint("decode failed")
                return []
            }
        }
        return []
    }
}