//如果粘贴的是纯数字的话，允许粘贴 否则不允许
//如果输入的非数字返回NO 否则返回YES
<pre>
if ([string rangeOfCharacterFromSet:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]].location != NSNotFound)
{
// BasicAlert(@"", @"This field accepts only numeric entries.");
return NO;
}
</pre>

可定制的方法
<pre>
NSCharacterSet * set = [[NSCharacterSet characterSetWithCharactersInString:@"0123456789."] invertedSet];
if ([string rangeOfCharacterFromSet:set].location != NSNotFound)
{
// BasicAlert(@"", @"This field accepts only numeric entries.");
return NO;
}

</pre>
Allow only Numbers for UITextField input
Check NSString for special characters