Question

I am trying to set up my uitableview for indexing, I have got number of sections working fine, now and the data is in the NSDictionary heres my output with nslog —>

Dictionary: {
    H =     (
        Honda,
        Honda,
        Honda,
        Honda,
        Honda,
        Honda,
        Honda
    );
    M =     (
        Mazda,
        Mazda,
        Mitsubishi,
        Mitsubishi,
        Mitsubishi,
        Mitsubishi,
        Mitsubishi,
        Mitsubishi
    );
    N =     (
        Nissan,
        Nissan,
        Nissan,
        Nissan,
        Nissan,
        Nissan,
        Nissan
    );
    T =     (
        Toyota,
        Toyota,
        Toyota
    );

I am now trying to set up my table like so

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return the number of sections.
    return [arraysByLetter count];
    //return 0;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // Return the number of rows in the section.
    return [[arraysByLetter objectAtIndex:section] count];
    //return 1;
}

however I am getting a warning ‘NSMutableDictionary’ may not respond to ‘objectAtIndex:’ inside my numberOfRowsInSection delegate method… How do I get around this?

Answer 1

You cannot index a dictionary as you would an array. You access dictionaries using keys. NSDictionary does provide two methods for getting arrays: allKeys and allValues.

I’m not sure what you are trying to accomplish, but if you want to organize the car makers alphabetically, you can get all the keys ([arraysByLetter allKeys]), sort them alphabetically, and then index into that sorted array. When you actually get the car makers’ names you will then use objectForKey: to load the array of makers.

Update:
Assuming a sorted array named sortedLetters, you can change your numberOfRowsInSection to the following:

NSString *currentLetter = [sortedLetters objectAtIndex:section];
return [[arraysByLetter objectForKey:currentLetter] count];

You probably want to setup the sortedLetters array on initialization, unless it is dynamic.