ios - 在 .xib 所有者的 ViewController 中为 textField 设置委托(delegate)

Question

我正在尝试使用 xib 文件来显示自定义更改 View 。为此，我使用 here 中的 SimpleAlert。我有 .xib 文件，其中包含我的文本字段，作为 .xib 的所有者，我设置了 ViewController。

import UIKit

class TestBaumViewController: UIViewController, UITextFieldDelegate {

@IBOutlet weak var tfFirst: UITextField!
@IBOutlet weak var tfSecond: UITextField!
@IBOutlet weak var tfThird: UITextField!
@IBOutlet weak var tfFourth: UITextField!


init() {
    super.init(nibName: "TestBaumViewController", bundle: nil)
    initializeTextFields()
}

required init(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
}

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
    //initializeTextFields()
}

override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)
    //initializeTextFields()
}

override func awakeFromNib() {
    super.awakeFromNib()
    //initializeTextFields()
}

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

func initializeTextFields() {
    tfFirst.delegate = self // Error Here!
    tfFirst.keyboardType = UIKeyboardType.ASCIICapable
    
    tfSecond.delegate = self
    tfSecond.keyboardType = UIKeyboardType.NumberPad
    
    tfThird.delegate = self
    tfThird.keyboardType = UIKeyboardType.ASCIICapable
    
    tfFourth.delegate = self
    tfFourth.keyboardType = UIKeyboardType.NumberPad
}

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    var result = true
    let prospectiveText = (textField.text as NSString).stringByReplacingCharactersInRange(range , withString: string)
    
    if textField == tfFirst {
        if count(string) > 0 {
            let disallowedCharacterSet = NSCharacterSet(charactersInString: "BW").invertedSet
            let replacementStringIsLegal = string.rangeOfCharacterFromSet(disallowedCharacterSet) == nil
        
            let resultingStringLengthIsLegal = count(prospectiveText) <= 1
        
            result = replacementStringIsLegal && resultingStringLengthIsLegal
        }
    }
    
    if textField == tfSecond {
        if count(string) > 0 {
            let disallowedCharacterSet = NSCharacterSet(charactersInString: "0123456789").invertedSet
            let replacementStringIsLegal = string.rangeOfCharacterFromSet(disallowedCharacterSet) == nil
            
            let resultingStringLenthIsLegel = count(prospectiveText) <= 3
            
            result = replacementStringIsLegal && resultingStringLenthIsLegel
        }
    }
    
    if textField == tfThird {
        if count(string) > 0 {
            let disallowedCharacterSet = NSCharacterSet(charactersInString: "abcdefghijklmnopqrstuvwxyz").invertedSet
            let replacementStringIsLegal = string.rangeOfCharacterFromSet(disallowedCharacterSet) == nil
            
            let resultingStringLenthIsLegel = count(prospectiveText) <= 1
            
            result = replacementStringIsLegal && resultingStringLenthIsLegel
        }
    }
    
    if textField == tfFourth {
        if count(string) > 0 {
            let disallowedCharacterSet = NSCharacterSet(charactersInString: "0123456789").invertedSet
            let replacementStringIsLegal = string.rangeOfCharacterFromSet(disallowedCharacterSet) == nil
            
            let resultingStringLenthIsLegel = count(prospectiveText) <= 3
            
            result = replacementStringIsLegal && resultingStringLenthIsLegel
        }
    }
    return result
}

如您所见，我为我的文本字段添加了 IBOutlets，现在我想将此 View Controller 添加为它们的委托(delegate)。这样我就可以检查文本字段中输入的内容。

我尝试了不同的方法。首先，我尝试将 textfield.delegate = self 放入 viewDidLoad 方法中，但出现错误“ fatal error :在展开可选值时意外发现 nil”，我认为这是因为文本字段不是创建喷气机。接下来它尝试了 viewDidAppear 方法，结果相同。最后，在我将一个对象添加到 .xib 并将 View Controller 类设置为其类以触发 awakeFromNib 方法之后，我将 textfield.delegate = self 放入该方法中。但我在这里遇到同样的错误。

是否有我没有想到的事情，或者我正在做的事情不会奏效？

问候阿达卡斯

Answer 1

因为您已经声明您的 Controller 符合 UITextFieldDelegate 协议(protocol)，所以在 Interface Builder 中执行此操作:

1. 选择你的文本框
2. 显示连接检查器
3. 将有一个 Outlets 部分，其下有 delegate。
4. 将 delegate 右侧的圆圈拖到您的 View Controller 对象中，如下所示

1. 对每个文本字段执行此操作

现在应该正确调用 textField 委托(delegate)方法。