很多情況下，一下輸入框需要按照要求進(jìn)行輸入，輸入內(nèi)容由開發(fā)人員來(lái)指定。例如：密碼輸入框只能輸入純數(shù)字或者是拼音與數(shù)字結(jié)合的文本等，那么我們?cè)陂_發(fā)的時(shí)候就需要做一些輸入文本的限時(shí)。

一、只能輸入純數(shù)字

在這里以UITextField為例：其實(shí)現(xiàn)代碼如下：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    return [self validateNumber:string];
}

- (BOOL)validateNumber:(NSString*)number {
    BOOL res = YES;
    NSCharacterSet* tmpSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789"];
    int i = 0;
    while (i < number.length) {
        NSString * string = [number substringWithRange:NSMakeRange(i, 1)];
        NSRange range = [string rangeOfCharacterFromSet:tmpSet];
        if (range.length == 0) {
            res = NO;
            break;
        }
        i++;
    }
    return res;
}

另外我們還有一種更加簡(jiǎn)便的方法來(lái)實(shí)現(xiàn)這一目的：
首先宏定義

#define NUMBER @"0123456789"

接著

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:NUMBER] invertedSet];
    NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
    return [string isEqualToString:filtered];
}

二、只能輸入純大小寫字母

和以上只能輸入純數(shù)字類似，實(shí)現(xiàn)起來(lái)簡(jiǎn)單，只需要宏定義

#define LETTER @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

然后實(shí)現(xiàn)

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:LETTER] invertedSet];
    NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
    return [string isEqualToString:filtered];
}

三、大小寫字母和數(shù)字結(jié)合輸入

對(duì)照以上

#define LETTER_NUMBER @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

同樣道理具體能夠輸入那些內(nèi)容如果輸入內(nèi)容能夠一一列舉的話我們就可以通過(guò)define來(lái)設(shè)置了，實(shí)現(xiàn)起來(lái)超簡(jiǎn)單。

限制只能輸入中文

在這里用到了觀察者

- (void)viewDidLoad {
    [super viewDidLoad];
    _myTextField.delegate = self;
    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(textFiledEditChanged:) name:UITextFieldTextDidChangeNotification object:_myTextField];

}
- (BOOL)textFieldShouldReturn:(UITextField *)textField{
    [textField resignFirstResponder];
    
    //過(guò)濾非漢字字符
    textField.text = [self filterCharactor:textField.text withRegex:@"[^\u4e00-\u9fa5]"];
    
    if (textField.text.length >= 4) {
        textField.text = [textField.text substringToIndex:4];
        
    }
    return NO;
}

- (void)textFiledEditChanged:(id)notification{
    
    UITextRange *selectedRange = _myTextField.markedTextRange;
    UITextPosition *position = [_myTextField positionFromPosition:selectedRange.start offset:0];
    
    if (!position) { //// 沒(méi)有高亮選擇的字
        //過(guò)濾非漢字字符
        _myTextField.text = [self filterCharactor:_myTextField.text withRegex:@"[^\u4e00-\u9fa5]"];
        
        if (_myTextField.text.length >= 4) {
            _myTextField.text = [_myTextField.text substringToIndex:4];
        }
    }else { //有高亮文字
        //do nothing
    }
}

- (NSString *)filterCharactor:(NSString *)string withRegex:(NSString *)regexStr{
    NSString *searchText = string;
    NSError *error = NULL;
    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:regexStr options:NSRegularExpressionCaseInsensitive error:&error];
    NSString *result = [regex stringByReplacingMatchesInString:searchText options:NSMatchingReportCompletion range:NSMakeRange(0, searchText.length) withTemplate:@""];
    return result;
}

- (void)dealloc{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

如果要限制輸入字符位數(shù)的話可以直接設(shè)置，這個(gè)實(shí)現(xiàn)上有很多種，最簡(jiǎn)單的就是

- (void)textViewDidChange:(UITextView *)textView{
    NSInteger number = [textView.text length];
    if (number > 300) {
        textView.text = [textView.text substringToIndex:300];
    }
}