注册功能的键盘限制输入

在最近的项目注册功能模块, 对于键盘输入限制(只能输入字母,数字,禁止输入一切的特殊符号)

首先我们要设置textfield的代理<UITextFieldDelegate>
先定义下面的这个宏:

#define ALPHANUM @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

然后写代理方法

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