通常我們需要限制輸入數字 字元 字母 或者中文等等
一般情況我們用到textfiled的代理方法去做

//
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{

    NSCharacterSet *charer = [NSCharacterSet characterSetWithCharactersInString:@"12345"];
    NSString *filed  = [[string componentsSeparatedByCharactersInSet:charer] componentsJoinedByString:@""
 
];
    if ([filed isEqualToString:string]) {
        return NO;
    }
    return yes;
}

這樣就可以限制只輸入 字串裡給出的字元

分享一個
限制只輸入數字金額,並且限制輸入最大數字,且自動判斷輸入0後變為小數點的方法

步驟.
設定textfiled的delegate = self;

//
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString
 
 *)string{


    return [ViewController moneyTextField:textField shouldChangeCharactersInRange:range replacementString:string max:1000];
}



#pragma mark - 限制輸入數字以及最大值 方法實現
+(BOOL)moneyTextField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string max:(NSInteger
 
)max
{
    //篩選輸入內容確保正確性
    NSCharacterSet *characterSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789.\b"];
    string = [string stringByReplacingOccurrencesOfString:@" " withString:@""];
    if ([string rangeOfCharacterFromSet:[characterSet invertedSet]].location != NSNotFound) {
        return NO;
    }

    BOOL isHasRadixPoint = YES;
    //小數點後面的位數
    NSInteger RadixPointNum = 2;
    NSString *existText = textField.text;
    //判斷是否含有小數點
    if ([existText rangeOfString:@"."].location == NSNotFound) {
        isHasRadixPoint = NO;
    }

    if (string.length > 0) {
        unichar newChar = [string characterAtIndex:0];
        //開始進入判斷文字
        if (existText.length>0) {
            if ([existText characterAtIndex:0]=='0') {
                //當首位是0的時候
                if (newChar=='0') {
                    //輸入是零的時候判斷是否有小數點
                    if (isHasRadixPoint) {
                        return range.location<=2;
                    }else{
                        return NO;
                    }
                }else if((newChar > '0' && newChar <= '9') &&existText.length<=1){
                    textField.text = @"";
                }
            }
        }

        if ((newChar >= '0' && newChar <= '9') || newChar == '.' ) {
            if (newChar == '.') {
                if (existText.length==0) {
                    textField.text = @"0.";
                    return NO;
                }else{
                    return !isHasRadixPoint;
                }
            }else {
                if (isHasRadixPoint) {
                    NSRange ran = [existText rangeOfString:@"."];
                    return (range.location - ran.location <= RadixPointNum);
                } else{
                    //小數點前面的位數
                    //return existText.length<6;
                    if ([textField.text isEqualToString:@"0"]){
                        textField.text = @"0.";
                    }
                    NSString *nowString;
                    if (range.length==0) {
                        nowString = [NSString stringWithFormat:@"%@%@",textField.text,string];
                    }else{
                        nowString = [textField.text stringByReplacingCharactersInRange:range withString:string];
                    }
                    //                    NSString *nowString = [textField.text stringByReplacingCharactersInRange:range withString:string];
                    if (nowString.doubleValue>= max) {
                        textField.text = [NSString stringWithFormat:@"%ld",max];
                        return NO;
                    }
                    return nowString.doubleValue <= max;
                }
            }
        }else {
            return YES;
        }
    }
    return YES;
}