Question

我将textview中的值保存到像这样的coredata

let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let newAttr = NSEntityDescription.insertNewObject(forEntityName: "TableName", into: context )

let attribute_name = textView.text

newAttr.setValue(attribute_name, forKey "attr_name")

context.save()

然后我试着像这样读回来：

let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let fetchRequest: NSFetchRequest = TableName.fetchRequest()

let cdRowsArr = try context.fetch(fetchRequest)
let cdRow = cdRows[0]
let txtViewDesc = String(describing: cdRow.value(forKey: "attr_name"))
let attrs = [NSFontAttributeName : UIFont.boldSystemFont(ofSize:15)]
let boldString = NSMutableAttributedStrign(string: txtViewDesc, attributes: attrs)
textView.attributedText = boldString

由于某种原因，每次输出都是Optional（“originalTextValue”）或nil，如果它是空的

我不明白为什么我想要的值被可选的

包围

Answer 1

因为var将被声明为可选。使用此代码来获取变量的访问值。

if let value = originalTextValue{
 //use value here now it wont be optional.
 print(value)
}

Answer 2

替换此行：

let attribute_name = textView.text

用这个：

let attribute_name = textView.text ?? ""

它应该解决这个可选问题。如果它仍然不起作用，那么也替换这一行：

let txtViewDesc = String(describing: cdRow.value(forKey: "attr_name"))

使用：

let txtViewDesc = String(describing: cdRow.value(forKey: "attr_name") ?? "")

Swift 3可选附加到String

2 个答案: