讓UITextField只接受Swift中的小字母字母？

Question

我想使textField只接受小字母不是大寫字母，也不接受任何特殊符號或沒有任何數字。

Answer 1

您可以使用正則表達式的，例如下面的正則表達式，只允許小符號

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool { 
    if string.isEmpty { 
     return true 
    } 
    let regex = "[a-z]{1,}" 
    return NSPredicate(format: "SELF MATCHES %@", regex).evaluate(with: string) 
} 

Answer 2

限制大寫字母，數字&特殊符號，返回false除文本視圖中的小寫字母委託方法textField:shouldChangeCharactersInRange:。

雨燕3.0：

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool { 
     var myCharSet = CharacterSet(charactersInString: "abcdefghijklmnopqrstuvwxyz") 
     for i in 0..<(string.characters.count ?? 0) { 
      var c: unichar = string[i] 
      if !myCharSet.characterIsMember(c) { 
       return false 
      } 
     } 
     return true 
    } 

Answer 3

檢查此更新的代碼：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{ 
    NSLog(@"textField:shouldChangeCharactersInRange:replacementString:"); 
     NSCharacterSet *myCharSet = [NSCharacterSet characterSetWithCharactersInString:@"abcdefghijklmnopqrstuvwxyz"]; 
     for (int i = 0; i < [string length]; i++) 
     { 
      unichar c = [string characterAtIndex:i]; 
      if (![myCharSet characterIsMember:c]) 
      { 
       return NO; 
      } 
     } 

     return YES; 
    } 

} 

斯威夫特

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool { 

     let set = NSCharacterSet(charactersInString: "abcdefghijklmnopqrstuvwxyz").invertedSet 
     return string.rangeOfCharacterFromSet(set) == nil 

    }    

Answer 4

嘗試下面的代碼只是自動獲得小寫字母這一點。

import UIKit 

class ViewController: UIViewController { 
    @IBOutlet weak var textEntry: UITextField! 

    //MARK : - Life Cycle 
    override func viewDidLoad() { 
     super.viewDidLoad() 
     textEntry.addTarget(self, action: #selector(self.textFieldDidChange), for: .editingChanged) 
    } 

    //MARK: - Lower letter function 
    func textFieldDidChange(sender: UITextField) { 
     sender.text = sender.text?.lowercased() 
     print(textEntry.text ?? "") //Check your text output here 
    } 
} 

Answer 5

您可以使用此也

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool { 

    // Return false when user tries to delete but textField is empty 
    let currentCharacterCount = textField.text?.characters.count ?? 0 
    if (range.length + range.location > currentCharacterCount) { 
     return false 
    } 

    // Return true when user tries to delete but textField is not empty 
    if string == "" { 
     return true 
    } 

    let userEnteredString = textField.text ?? "" 
    let newString = (userEnteredString as NSString).replacingCharacters(in: range, with: string) as NSString 

    return ((newString as String).range(of: "^[a-z]+$", options: .regularExpression) != nil) 

}