TextInputView

设计灵感来源于 Android 的 ViewGroup 类，从设计模式的角度来看，这是一个对象适配器模式（可以理解为装饰(Decorator)模式/代理(Proxy)模式等），通过创建一个包装类持有 UITextView/UITextField 等的一个实例，实现被封装类的功能扩展。

示例代码

import UIKit

class ViewController: UIViewController {

@IBOutlet weak var textView: TIVTextView!
@IBOutlet weak var textField: TIVTextField!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    textView.delegate = self;
    textView.placeHolderText = NSAttributedString(string: "请输入评论， 不超过20个字", attributes: [NSFontAttributeName: UIFont.systemFontOfSize(12), NSForegroundColorAttributeName: UIColor.whiteColor()])
    textField.tipLabel.font = UIFont.systemFontOfSize(16, weight: UIFontWeightLight)
    textField.tipLabelHeight = 18;

    textField.delegate = self
    textField.placeHolderText = NSAttributedString(string: "请输入评论， 不超过20个字", attributes: [NSFontAttributeName: UIFont.systemFontOfSize(12), NSForegroundColorAttributeName: UIColor.whiteColor()])
    textField.tipLabel.font = UIFont.systemFontOfSize(8, weight: UIFontWeightLight)
    textField.tipLabelHeight = 10;
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
}

}

extension ViewController:TIVTextFieldDelegate{ func textField(didChanged textField: TIVTextField) -> (String, Bool) { let maxCount = self.maxAllowCharactersCount let currentTextCount = textField.currentText.characters.count

    let exccedCount = currentTextCount - maxCount;
    if exccedCount > 0{//excced the max
        return ("超过\(exccedCount)个文字", true)
    }else{
        return ("", false)
    }
}

}

extension ViewController:TIVTextViewDelegate{

var maxAllowCharactersCount:Int {
    get{
        return 20
    }
}

func textView(didBeginEditing textView:TIVTextView){
    print("text view did begin editing")
}

func textView(didEndEditing textView:TIVTextView){
    print("text view did end editing")
}

func textView(shouldEndEditing  textView:TIVTextView) -> Bool{
    return true
}

func textView(didChanged textView:TIVTextView) -> (String, Bool){
    let maxCount = self.maxAllowCharactersCount
    let currentTextCount = textView.currentText.characters.count

    let exccedCount = currentTextCount - maxCount;
    if exccedCount > 0{//excced the max
        return ("超过\(exccedCount)个文字", true)
    }else{
        return ("", false)
    }
}

}