- 优点，简单易用。
- 缺点，未经测试。不能再次使用代理，需要自己添加回调函数实现。
extension UITextView: UITextViewDelegate {
var xColor: (textColor: UIColor, placeHolderColor: UIColor)? {
set {
textColor = newValue?.placeHolderColor
objc_setAssociatedObject(self, UnsafeRawPointer(bitPattern: #function.hashValue)!, newValue, .OBJC_ASSOCIATION_COPY_NONATOMIC)
}
get {
let obj: (UIColor, UIColor)? = objc_getAssociatedObject(self, UnsafeRawPointer(bitPattern: #function.hashValue)!) as? (UIColor, UIColor)
return obj
}
}
var placeHolder: String? {
set {
delegate = self
text = newValue
objc_setAssociatedObject(self, UnsafeRawPointer(bitPattern: #function.hashValue)!, newValue, .OBJC_ASSOCIATION_COPY_NONATOMIC)
}
get {
let obj: String? = objc_getAssociatedObject(self, UnsafeRawPointer(bitPattern: #function.hashValue)!) as? String
return obj ?? ""
}
}
public func textViewShouldBeginEditing(_ textView: UITextView) -> Bool {
if textView.text == placeHolder {
textView.text = ""
textView.textColor = xColor?.textColor
}
return true
}
public func textViewShouldEndEditing(_ textView: UITextView) -> Bool {
if textView.text == "" {
textView.text = placeHolder
textView.textColor = xColor?.placeHolderColor
}
return true
}
}
