NSMutableArray index 1 beyond bounds [0 .. 0]

Question

I am messing up with JSON and NSMutablearray. Of course I am a beginner.

I have this code, taken and modified for my purposes from an online tutorial:

[This is the .m file]
- (void) downloadItems {

    // Download the json file
    NSURL *jsonFileUrl = [NSURL URLWithString:@"http://example.com/service.php"];

    // Create the request
    NSURLRequest *urlRequest = [[NSURLRequest alloc] initWithURL:jsonFileUrl];

    // Create the NSURLConnection
    [NSURLConnection connectionWithRequest:urlRequest delegate:self];

}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    // Initialize the data object
    datiScaricati = [[NSMutableData alloc] init];

}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    // Append the newly downloaded data
    [datiScaricati appendData:data];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {

    // Create an array to store the locations
    NSMutableArray *frasiMemorizzate = [[NSMutableArray alloc] init];

    // Parse the JSON that came in
    NSError *error;
    NSArray *jsonArray = [NSJSONSerialization JSONObjectWithData:datiScaricati options:NSJSONReadingAllowFragments error:&error];


    // Loop through Json objects, create question objects and add them to our questions array
    for (int i = 0; i < jsonArray.count; i++)
    {
        NSDictionary *jsonElement = jsonArray[i];

        // Create a new location object and set its props to JsonElement properties
        Frase *nuovaFrase = [[Frase alloc] init];
        nuovaFrase.fraseDelDatabase = jsonElement[@"Frase"];

        NSLog(@"Phrase read from database: %@", nuovaFrase.fraseDelDatabase);

        // Add this question to the locations array
        [frasiMemorizzate addObject:nuovaFrase.fraseDelDatabase];

        NSLog(@"Phrases stored in the array: %@", frasiMemorizzate);


        prova = [frasiMemorizzate objectAtIndex:0];

        NSLog(@"Phrases at index 0: %@",prova);

    }


}

NSLog gives this:

2014-06-15 11:05:28.705 ProvaMySql[13805:60b] Phrase read from database: Frase uno, Prova!
2014-06-15 11:05:28.706 ProvaMySql[13805:60b] Phrases stored in the array: (
    "Frase uno, Prova!"
)
2014-06-15 11:05:28.706 ProvaMySql[13805:60b] Phrases at index 0: Frase uno, Prova!
2014-06-15 11:05:28.707 ProvaMySql[13805:60b] Phrase read from database: Frase due, Prova!
2014-06-15 11:05:28.707 ProvaMySql[13805:60b] Phrases stored in the array: (
    "Frase uno, Prova!",
    "Frase due, Prova!"
)
2014-06-15 11:05:28.708 ProvaMySql[13805:60b] Phrases at index 0: Frase uno, Prova!
2014-06-15 11:05:28.708 ProvaMySql[13805:60b] Phrase read from database: Frase tre, Prova!!
2014-06-15 11:05:28.709 ProvaMySql[13805:60b] Phrases stored in the array: (
    "Frase uno, Prova!",
    "Frase due, Prova!",
    "Frase tre, Prova!!"
)
2014-06-15 11:05:28.709 ProvaMySql[13805:60b] Phrases at index 0: Frase uno, Prova!

So, I think that I am getting data one by one from database ("frase uno", then "frase due", then "frase tre"). And I see also that the array is populating (Phrased stored in the array:)

When I am calling

prova = [frasiMemorizzate objectAtIndex:0];

        NSLog(@"Phrases at index 0: %@",prova);

I get: "Frase uno", that is what I should expect, but if I use "objectAtIndex:1" I have that error: index 1 beyond bounds [0 .. 0], but I expected to have the second phrase: "Frase Due".

I'd like to know why and the right way to get the data I need, and, maybe, as you are replying my question, how can I Know how many items are stored in a Mutable Array, to non call unallocated index position!

Thanks for your patience!

Answer 1

Error is thrown because you try to access second index in the array when there is only one object.

Make this little change and it works:

    prova = [frasiMemorizzate objectAtIndex:i];

    NSLog(@"Phrases at index %d: %@", i, prova);