UITextField 限制只能输入价格形式内容

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
   NSString * str = [NSString stringWithFormat:@"%@%@",textField.text,string];//匹配以0开头的数字
   NSPredicate * predicate0 = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",@"^[0][0-9]+$"];//匹配两位小数、整数
   NSPredicate * predicate1 = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",@"^(([1-9]{1}[0-9]*|[0])\.?[0-9]{0,2})$"];

   return ![predicate0 evaluateWithObject:str] && [predicate1 evaluateWithObject:str] ? YES : NO;
}