无法读取和格式化日期

Posted 2023-02-23

【中文标题】无法读取和格式化日期

【英文标题】：Trouble Reading and Formatting Date

【发布时间】：2020-10-08 23:37:52

【问题描述】：

我正在尝试将 CoreData 中的一些数据读取到标准列表中，但在读取和格式化日期时遇到了问题。我似乎在杂草中遥遥无期！我有错误“'日期类型的值？'没有成员 'getFormattedDate'”，我试图在 getFormattedDate 函数的最后一行显示日期和错误“无法将 'listView' 类型的值转换为预期的参数类型 'Date'”。

struct listView: View 
    
    @Environment(\.managedObjectContext) private var viewContext
    
    let categories = ["AAA", "BBB","CCC","DDD"]
    
    @FetchRequest(
        entity: CurrTrans.entity(),
        sortDescriptors: []
    ) var currTrans: FetchedResults<CurrTrans>
    
    var body: some View 
        
        List 
            ForEach(currTrans, id: \.self)  item in
                VStack 
                    let date = item.entryDT
                    Text(date.getFormattedDate())
                      
                    // display category
                    if item.entryCat != nil 
                        Text("Category: \(categories[Int(item.entryCat)])")
                     else 
                        Text("")
                    
                    // display description
                    if item.entryDsc != nil 
                        Text("\(item.entryDsc!)")
                     else 
                        Text("")
                    
                
            
        
    
    
        func getFormattedDate() -> String 
            let dateformat = DateFormatter()
            dateformat.dateFormat = "d MMM HH:mm"
            return dateformat.string(from: self)
        
    

【参考方案1】：

@objc(Transaction)
public class Transaction: NSManagedObject 
    static let categoryStringsByCategoryID = ["AAA", "BBB","CCC","DDD"]
    func categoryString() -> String
         return Transaction.categoryStringsByCategoryID[self.categoryID]
    


struct ListView: View 
    
    @Environment(\.managedObjectContext) private var viewContext
    
    @FetchRequest(sortDescriptors: []) var transactions: FetchedResults<Transaction>
    
    var body: some View 
        
        List 
            ForEach(transactions)  transaction in
                VStack 
                    Text("\(transaction.timestamp!, formatter: transactionFormatter)")
                    // display category
                    
                    Text("Category: \(transaction.categoryString)")
                    
                    // display description
                    Text("\(transaction.entryDescription ?? "")")
                
            
        
    


private let transactionFormatter: DateFormatter = 
    let formatter = DateFormatter()
    formatter.dateStyle = .short
    formatter.timeStyle = .medium
    return formatter
()