How would you scan an array of strings for a set of substrings in objective-c?

Question

So I basically have an array of words and phrases. Some of them contain curses. I want to create a method that automatically scans each of the units in the array for curses. If

Answer 1

As you state you are:

appalled that I have not been able to find a method of NSString that will search for a bunch of words at the same time

though this seems a strange reaction - programming is about building solutions after all, here is a solution which searches for all the words at the same time using a single method, but belonging to NSRegularExpression rather than NSString.

Our sample data:

NSArray *sampleLines = @[@"Hey how are you",
                         @"What is going on?",
                         @"What’s up dude?",
                         @"Do you want to get chipotle?",
                         @"They are the youth"
                         ];
NSArray *stopWords = @[@"you", @"hey"];

The last sample line to check we don't match partial words. Capitalisation added to test for case insensitive matching.

We construct a RE to match any of the stop words:

• \b - word boundary, options set to use Unicode word boundaries in this example
• (?: ... ) - a non-capturing group, just used as it is slightly faster than a capturing one and it will be the same as the whole match anyway
• | - or

Pattern for exmaple stop words: \b(?:you|hey)\b

// don't forget to use \\ in a string literal to insert a backslash into the pattern
NSString *pattern = [NSString stringWithFormat:@"\\b(?:%@)\\b", [stopWords componentsJoinedByString:@"|"]];
NSError *error = nil;
NSRegularExpression *stopRE = [NSRegularExpression regularExpressionWithPattern:pattern
                                                                        options:(NSRegularExpressionCaseInsensitive | NSRegularExpressionUseUnicodeWordBoundaries)
                                                                          error:&error];
// always check error returns
if (error)
{
    NSLog(@"RE construction failed: %@", error);
    return;
}

Iterate through sample lines checking if they contain a stop word or not and display result on console:

for (NSString *aLine in sampleLines)
{
    // check for all words anywhere in line in one go
    NSRange match = [stopRE rangeOfFirstMatchInString:aLine
                                              options:0
                                                range:NSMakeRange(0, aLine.length)];
    BOOL containsStopWord = match.location != NSNotFound;
    NSLog(@"%@: %@", aLine, containsStopWord ? @"Bad" : @"OK");
}

Regular expression matching should be efficient, and as the example never copies individual words or matches as NSString objects this should not create a lot of temporary objects as methods which enumerate the individual words do.

HTH