UITextField - 將文字欄位限制為某些字元

如果要對文字欄位執行使用者輸入驗證，請使用以下程式碼段：

// MARK: - UITextFieldDelegate

let allowedCharacters = CharacterSet(charactersIn:"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvxyz").inverted    

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    
    let components = string.components(separatedBy: allowedCharacters)
    let filtered = components.joined(separator: "")
    
    if string == filtered {
        
        return true

    } else {
        
        return false
    }
}

Objective-C

#define ACCEPTABLE_CHARACTERS @"0123456789 ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string  
{
      NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:ACCEPTABLE_CHARACTERS] invertedSet];

      NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];

      return [string isEqualToString:filtered];
}

此外，你還可以使用 apple 提供的字符集來執行驗證：

請檢視 https://developer.apple.com/reference/foundation/nscharacterset

let allowedCharacters = CharacterSet.alphanumerics.inverted
let allowedCharacters = CharacterSet.capitalizedLetters.inverted