使用rangeOfString和textfield shouldChangeCharactersInRange-删除字符？

Question

I'm using rangeofString and textfield: shouldChangeCharactersinRange: to restrict the types of keystrokes that will be valid in a textfield.

-(BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{


    NSString *includeString = @"1234567890-()+" ;

    if ([includeString rangeOfString:string].location == NSNotFound) {
        return NO;
    }

return YES;

}

this works fine EXCEPT i now can't use the delete key. Any ideas how to represent the delete key to add it to the includeString?

I tried

`NSString *includeString = @"1234567890-()+\\b"

but that didn't work - neither did it allow the \\ or b characters to appear which i thought odd

Thanks

Answer 1

The replacement string string is empty when characters are deleted. Since rangeOfString:string returns NSNotFound for an empty string, you have to check for that situation first:

-(BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{

    if ([string length] == 0)
        return YES;
    NSString *includeString = @"1234567890-()+" ;
    if ([includeString rangeOfString:string].location == NSNotFound) {
        return NO;
    }
    return YES;
}

Update: As @rmaddy correctly pointed out, the above method fails if more than one character is pasted into the text field. The following method checks if all characters of the replacement string are valid. (There are probably many solutions, this is only one of them.)

-(BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{

    static NSString *includeString = @"1234567890-()+";
    NSCharacterSet *includeSet = [NSCharacterSet characterSetWithCharactersInString:includeString];
    if ([[string stringByTrimmingCharactersInSet:includeSet] length] > 0)
        return NO;
    return YES;
}

Note that the empty string does not need to be handled separately anymore.