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import UIKitclass ViewController: UIViewController ,UITextFieldDelegate{ @IBOutlet weak var button: UIButton! @IBOutlet weak var textField: UITextField! override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view, typically from a nib. textField.delegate = self } func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool { let newText = textField.text .stringByReplacingCharactersInRange(range.toRange(textField.text), withString: string) button.enabled = countElements(newText) > 0 return true } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() // Dispose of any resources that can be recreated. }}//扩展NSRange，让swift的string能使用stringByReplacingCharactersInRangeextension NSRange { func toRange(string: String) -> Range<String.Index> { let startIndex = advance(string.startIndex, self.location) let endIndex = advance(startIndex, self.length) return startIndex..<endIndex }} |
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原文地址：http://www.cnblogs.com/Free-Thinker/p/4841061.html
