macos - 自定义 NSFormatter swift 返回 nil

Question

我在 Swift 中有一个 NSFormatter，它附加到 NSTextField。它可以防止输入非法字符，但是当我尝试访问下一个字段的值时，它给出了一个 nil 值。

下面是类:

class PSEntryNameFormatter : NSFormatter {
    override func stringForObjectValue(obj: AnyObject?) -> String? {

        if obj == nil {
            println("stringForObjectValue: obj is nil, returning nil")
            return nil
        }
        if let o = obj as? String {
                println("stringForObjectValue:  obj is string, returning \(o)")
                return o
            }

        println("stringForObjectValue: obj is not string, returning nil")
        return nil
    }

    override func getObjectValue(obj: AutoreleasingUnsafeMutablePointer<AnyObject?>, forString string: String, errorDescription error: AutoreleasingUnsafeMutablePointer<NSString?>) -> Bool {
        println("getObjectValue: \(string)")
        let obj = string
        return true
    }

    override func isPartialStringValid(partialString: String?, newEditingString newString: AutoreleasingUnsafeMutablePointer<NSString?>, errorDescription error: AutoreleasingUnsafeMutablePointer<NSString?>) -> Bool {
        if let s = partialString {
            var illegals : String = join("",s.componentsSeparatedByCharactersInSet(PSEntryNameFormatterCharacterSet))
            var goods = s.componentsSeparatedByCharactersInSet(NSCharacterSet(charactersInString: illegals))
            let newString : NSString = join("", goods)

            if String(newString) == s {
                println("isPartialStringValid: partial string ok")
                return true
            }
        }

        println("isPartialStringValid: partial string bad")
        return false
    }
}

这是我尝试访问的方式:

func control(control: NSControl, textShouldEndEditing fieldEditor: NSText) -> Bool {
    println("Text should end editing")
    if (control == nameTextField) {
        var name = nameTextField.objectValue as String
        setObjectName(name)
    }
    return true
}

为了调试，我添加了 println 语句，这是当文本字段设置为"template"然后我删除两个字符时发生的情况:

stringForObjectValue:  obj is string, returning Template
stringForObjectValue:  obj is string, returning Template
isPartialStringValid: partial string ok
getObjectValue: Templat
isPartialStringValid: partial string ok
getObjectValue: Templa

然后我按下回车键:

getObjectValue: Templa
Text should end editing 
getObjectValue: Templa
stringForObjectValue: obj is nil, returning nil
getObjectValue:
stringForObjectValue: obj is nil, returning nil
stringForObjectValue: obj is nil, returning nil
fatal error: unexpectedly found nil while unwrapping an Optional value

然后当我转换为字符串时它在线上崩溃了。显然我可以防止崩溃，但首先我想找出它返回 nil 的原因。非常感谢任何帮助!

Answer 1

问题出在您的 getObjectValue 函数中。

您应该以这种方式分配值:

obj.memory = string

代替

let obj = string