Question

I’m trying to detect the text in a text view whether it contains anything beyond a pattern of hex value \u00 - \u7f or not and then do something. Please take a look at this code:

NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"[\x00-\x7f]"
                                                                       options:NSRegularExpressionCaseInsensitive
                                                                         error:&error];
NSRange rangeOfFirstMatch = [regex rangeOfFirstMatchInString:textView.text
                                                     options:0 
                                                       range:NSMakeRange(0, [textView.text length])];

if (!NSEqualRanges(rangeOfFirstMatch, NSMakeRange(NSNotFound, 0)))
{
    // do statement 1
}
else
{
    // do statement 2
}

From above, if the text view contains both text inside and outside [\u00 - \u7f] this will do statement 1 but what I want is do statement 2.

In my opinion, it should have the regular expression opposite to this pattern but I don’t know what it is. Any suggestions are welcome, thank you.

Answer 1

A carat (‘^’) negates a character class, so [^\u00-\u7f] will match any character except those in the range ‘\u00’ through ‘\u7f’.

You could also use rangeOfCharacterFromSet: or canBeConvertedToEncoding: to check whether a string has any non-ASCII characters.

rangeOfCharacterFromSet:

NSRange ASCIIRange = NSMakeRange(0, 0x80);
NSCharacterSet *nonASCIICharSet = [[NSCharacterSet characterSetWithRange:ASCIIRange] invertedSet];
NSRange nonASCIIChars = [textView.text rangeOfCharacterFromSet:nonASCIICharSet];

if (nonASCIIChars.location == NSNotFound) {
    ...
} else {
    // textView.text contains non-ASCII characters
    ...
}

canBeConvertedToEncoding:

if ([textView.text canBeConvertedToEncoding:NSASCIIStringEncoding]) {
    ...
} else {
    // textView.text contains non-ASCII characters
    ...
}