How can I use an NSPredicate to select an exact phrase from an array?

Question

I am using an NSPredicate to filter an NSDictionary by a list of states and countries.

All the data are stored in a comma separated array: @"Alabama", @"Alaska", @"Arizona", @"Arkansas", @"California", @"Colorado", etc

However, there are 2 situations where duplicates are occurring. The state "New Mexico" contain the word "Mexico", and "Arkansas" contains the word "Kansas.

Here's the basic code I'm using to define the predicate.

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"Location contains[c] %@", @"Kansas"];

How can I make sure "Kansas" doesn't return objects with "Arkansas"? Using BEGINSWITH or LIKE doesn't work because the list begins with some other state.

Thanks!

Answer 1

Let's see if I understand correctly. You have a dictionary, where there is a key "Location" whose object is a string with comma separated state names. Sounds like you need a regular expression to match.

NSString* expr = [NSString stringWithFormat:@"^%1$@.*|.*, %1$@.*", @"Kansas"]  
NSPredicate* predicate = [NSPredicate predicateWithFormat:@"Location MATCHES[c] %@", expr];

Now, here is how it would behave for different examples:

@{@"Location": @"Kansas, Arkansas, Alabama"} //Pass
@{@"Location": @"Alabama, Kansas"} //Pass
@{@"Location": @"Arkansas, Alabama"} //Fail

---

The regular expression ^%1$@.*|.*, %1$@.* tests if the word provided is either at the start of the string or followed by characters and ", ", which puts it in the middle. %1$@ takes the first param, so that it can be used multiple times instead of prividing the same string several times.

Answer 2

May be this helps?

// If I understood correctly, then your locations in the dictionary are like this
NSString *locations = @"Alabama, Alaska, Arizona, Arkansas";

NSString *trimmedLocations = [locations stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
NSMutableArray *compoments = [[trimmedLocations componentsSeparatedByString:@","] mutableCopy];   
//now in components we have this: @[@"Alabama", @"Alaska", @"Arizona", @"Arkansas", @"California", @"Colorado"]

[compoments filterUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(NSString *evaluatedObject, NSDictionary *bindings) {
    return [evaluatedObject isEqualToString:@"Kansas"];
}]];

BOOL match = compoments.count;
if (match) {
    //do something with locations...
}