首先你的ViewController須要實現 UITextFieldDelegate 代理,swift
其次,須要字數限制的UITextField實例的代理要設置成 self(ViewController)spa
而後實現下列代理方法:代理
Objective—Ccode
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{blog
if(range.length + range.location > textField.text.length)string
{io
return NO;class
}方法
NSUInteger newLength = [textField.text length] + [string length] - range.length;di
return newLength <= 5;//最大字數長度
}
swift:
func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool { let currentCharacterCount = textField.text?.characters.count ?? 0 if (range.length + range.location > currentCharacterCount){ return false } let newLength = currentCharacterCount + string.characters.count - range.length return newLength <= 25 }