NSTextView 在粘贴前修改字符串

Question

我的目标是在将字符串粘贴到 NSTextView 之前修改字符串 - 删除所有非字母（数字、空格等）。

通过link，我想出了以下代码：

override func paste(_ sender: Any?) {
    let pasteboard = NSPasteboard.general
 // receive string from pasteboard
    if let pasteboardString = pasteboard.string(forType: .string) {
        let lettersOnly = CharacterSet.letters

     // filter the incoming string
        let lettersOnlyString = String(pasteboardString.unicodeScalars.filter { lettersOnly.contains($0) })

     // put back filtered string into pasteboard
        pasteboard.setString(lettersOnlyString, forType: .string)
        super.paste(sender)

     // put back initial formatted string
        pasteboard.setString(pasteboardString, forType: .string)
    }
}

lettersOnlyString确实是修改后的字符串，但最后还是粘贴了原始字符串，我仍然看到所有非字母字符。

我在这里错过了什么，也许这不是要走的路？也许我需要为此覆盖另一种方法？

Answer 1

我想我找到了答案，我必须在pasteboard.setString之前添加pasteboard.clearContents()。

为了完整起见，这是工作代码：

override func paste(_ sender: Any?) {
    let pasteboard = NSPasteboard.general

// get string from pasteboard
    if let pasteboardString = pasteboard.string(forType: .string) {
     // remove formatting from string
        let lettersOnly = CharacterSet.letters
        let lettersOnlyString = String(pasteboardString.unicodeScalars.filter { lettersOnly.contains($0) })

     // put modified string on pasteboard
        pasteboard.clearContents()
        pasteboard.setString(lettersOnlyString, forType: .string)

     // paste string from pasteboard as plain text
        pasteAsPlainText(sender)

     // put original string back on pasteboard
        pasteboard.clearContents()
        pasteboard.setString(pasteboardString, forType: .string)
    }
}

更新：

还可以更简单：

override func paste(_: Any?) {
    let pasteboard = NSPasteboard.general
    guard let pasteboardString = pasteboard.string(forType: .string),
        let validatedInput = validateInput(pasteboardString)
    else { return }

    insertText(validatedInput, replacementRange: NSMakeRange(NSNotFound, 0))
}

其中 validateInput() 是一个重构函数，用于过滤输入字符串。