判断UITextField的输入只为数字的方法
实现下面的委托

#define NUMBERS @"0123456789\n"

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
NSCharacterSet *cs;
if(textField == phoneNumberField)
{
cs = [[NSCharacterSet characterSetWithCharactersInString:NUMBERS] invertedSet];
NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
BOOL basicTest = [string isEqualToString:filtered];
if(!basicTest)
{
UIAlertView* alert = [[UIAlertView alloc] initWithTitle:@"提示"
message:@"请输入数字"
delegate:nil
cancelButtonTitle:@"确定"
otherButtonTitles:nil];

[alert show];
[alert release];
return NO;
}
}

//其他的类型不需要检测，直接写入
return YES;
}
如果输入的不是数字，进行提示。