Question

I’m having trouble making the sections in a UITableView. I’ve looked at the documentation for UILocalizedIndexedCollation as well as this sample code project:

https://developer.apple.com/library/ios/#samplecode/TableViewSuite/Listings/3_SimpleIndexedTableView_Classes_RootViewController_m.html#//apple_ref/doc/uid/DTS40007318-3_SimpleIndexedTableView_Classes_RootViewController_m-DontLinkElementID_18

What I have below is basically a straight copy/paste from the sample project. However, the sample project uses a custom object (TimeZoneWrapper.h) and then places the object in the correct section based on the object’s instance variable (TimeZoneWrapper.localeName). However, I’m not using custom objects. I’m using just a bunch of regular NSStrings. So my question is what method on NSString should I pass to the @selector() to compare and place the string in the correct section array?

Currently, I’m calling NSString’s copy method as a temporary hack to get things working (which it does), but I’m not sure if this is correct. A little explanation would be much appreciated!

- (void)configureSections {

// Get the current collation and keep a reference to it.
self.collation = [UILocalizedIndexedCollation currentCollation];

NSInteger index, sectionTitlesCount = [[collation sectionTitles] count]; // sectionTitles are A, B, C, etc.

NSMutableArray *newSectionsArray = [[NSMutableArray alloc] initWithCapacity:sectionTitlesCount];

// Set up the sections array: elements are mutable arrays that will contain the locations for that section.
for (index = 0; index < sectionTitlesCount; index++) {
    NSMutableArray *array = [[NSMutableArray alloc] init];
    [newSectionsArray addObject:array];
}

// Segregate the loctions into the appropriate arrays.
for (NSString *location in locationList) {

    // Ask the collation which section number the location belongs in, based on its locale name.
    NSInteger sectionNumber = [collation sectionForObject:location collationStringSelector:@selector(/* what do I put here? */)];

    // Get the array for the section.
    NSMutableArray *sectionLocations = [newSectionsArray objectAtIndex:sectionNumber];

    //  Add the location to the section.
    [sectionLocations addObject:location];
}

// Now that all the data's in place, each section array needs to be sorted.
for (index = 0; index < sectionTitlesCount; index++) {

    NSMutableArray *locationsArrayForSection = [newSectionsArray objectAtIndex:index];

    // If the table view or its contents were editable, you would make a mutable copy here.
    NSArray *sortedLocationsArrayForSection = [collation sortedArrayFromArray:locationsArrayForSection collationStringSelector:@selector(/* what do I put here */)];

    // Replace the existing array with the sorted array.
    [newSectionsArray replaceObjectAtIndex:index withObject:sortedLocationsArrayForSection];
}

self.sectionsArray = newSectionsArray;
}

Thanks in advance!

Answer 1

You should use @selector(self).

Using @selector(copy) will cause memory leaks in your project