如果用户增加价值，PDFkit表单会将数据传递给其他表单

Question

我使用此表单在我的iOS应用程序上创建pdf表单：

    // Intro: "Text2"
    let text2FieldNameBounds = CGRect(x: 154, y: pageBounds.size.height - 379, width: 427, height: 21)
    let text2FieldName = PDFAnnotation(bounds: text2FieldNameBounds, forType: PDFAnnotationSubtype(rawValue: PDFAnnotationSubtype.widget.rawValue), withProperties: nil)
    text2FieldName.widgetFieldType = PDFAnnotationWidgetSubtype(rawValue: PDFAnnotationWidgetSubtype.text.rawValue)
    text2FieldName.backgroundColor = UIColor.blue.withAlphaComponent(0.25)
    text2FieldName.font = UIFont(name: "ArialMT", size: 9)
    text2FieldName.maximumLength = 86
    text2FieldName.alignment = .left
    page.addAnnotation(text2FieldName)

我需要一些帮助，当用户在文本字段上书写内容时如何创建函数“ Hello”然后系统自动在text3FieldName上设置value =“ Hello Again”？