设置通知监听

- (void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    self.navigationController.navigationBar.hidden = YES;
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textFieldTextChanged:) name:UITextFieldTextDidChangeNotification object:nil];
}

- (void)viewWillDisappear:(BOOL)animated{
    [super viewWillDisappear:animated];
    self.navigationController.navigationBar.hidden = NO;
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UITextFieldTextDidChangeNotification object:nil];
}

设置代理

self.phoneTF.delegate = self;

#define PhoneTFLength 13

#pragma mark - textField 通知 监听

- (void)textFieldTextChanged:(NSNotification *)noti {
    UITextField *tf = noti.object;
    if (tf == self.phoneTF) {
        [self formatPhoneNumber:tf];
    }
}

#pragma mark - Delegate Methods

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
    previousTextFieldContent = textField.text;
    previousSelection = textField.selectedTextRange;
    if (range.location > PhoneTFLength-1){
        return NO;
    }
    return YES;
}

#pragma mark - help

- (void)formatPhoneNumber:(UITextField*)textField{
    NSUInteger targetCursorPosition = [textField offsetFromPosition:textField.beginningOfDocument toPosition:textField.selectedTextRange.start];
    NSString * nStr = [textField.text stringByReplacingOccurrencesOfString:@" " withString:@""];
    NSString* preTxt = [previousTextFieldContent stringByReplacingOccurrencesOfString:@" " withString:@""];
    char editFlag = 0;// 正在执行删除操作时为0，否则为1
    if (nStr.length <= preTxt.length) {
        editFlag = 0;
    }else{
        editFlag = 1;
    }
    if (nStr.length > 11) {
        textField.text = previousTextFieldContent;
        textField.selectedTextRange = previousSelection;
        return;
    }
    NSString* spaceStr = @" ";
    NSMutableString *mStrTemp = [NSMutableString string];
    int spaceCount = 0;
    if (nStr.length < 3 && nStr.length > -1) {
        spaceCount = 0;
    }else if (nStr.length < 7&& nStr.length > 2){
        spaceCount = 1;
    }else if (nStr.length < 12&& nStr.length > 6){
        spaceCount = 2;
    }
    for (int i = 0; i < spaceCount; i++){
        if (i == 0) {
            [mStrTemp appendFormat:@"%@%@", [nStr substringWithRange:NSMakeRange(0, 3)],spaceStr];
        }else if (i == 1){
            [mStrTemp appendFormat:@"%@%@", [nStr substringWithRange:NSMakeRange(3, 4)], spaceStr];
        }else if (i == 2){
            [mStrTemp appendFormat:@"%@%@", [nStr substringWithRange:NSMakeRange(7, 4)], spaceStr];
        }
    }

    if (nStr.length == 11){
        [mStrTemp appendFormat:@"%@%@", [nStr substringWithRange:NSMakeRange(7, 4)], spaceStr];
    }

    if (nStr.length < 4 && nStr.length > 0){
        [mStrTemp appendString:[nStr substringWithRange:NSMakeRange(nStr.length-nStr.length % 3,nStr.length % 3)]];
    }else if(nStr.length > 3){
        NSString *str = [nStr substringFromIndex:3];
        [mStrTemp appendString:[str substringWithRange:NSMakeRange(str.length-str.length % 4,str.length % 4)]];
        if (nStr.length == 11){
            [mStrTemp deleteCharactersInRange:NSMakeRange(13, 1)];
        }
    }
    textField.text = mStrTemp;
    // textField设置selectedTextRange
    NSUInteger curTargetCursorPosition = targetCursorPosition;// 当前光标的偏移位置
    if (targetCursorPosition == 9 || targetCursorPosition == 4){
        if (editFlag == 0){//删除
            curTargetCursorPosition = targetCursorPosition - 1;
        }else {//添加
            curTargetCursorPosition = targetCursorPosition + 1;
        }
    }

    UITextPosition *targetPosition = [textField positionFromPosition:[textField beginningOfDocument] offset:curTargetCursorPosition];
    [textField setSelectedTextRange:[textField textRangeFromPosition:targetPosition toPosition :targetPosition]];
}