UIPickerView empty with data source as JSON array

Question

I'm trying to populate a UIPickerView with JSON data that is parsed into an NSArray.

The console shows that the JSON is parsing properly but the UIPickerView is remaining empty.

Here's my code:

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView 
{
    return 1;
}

-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    //set number of rows
    return self.terrainJsonArray.count;
}

-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    //set item per row
    return [self.terrainJsonArray objectAtIndex:row];
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Parse JSON 

    NSString *terrainString = [NSString stringWithFormat:@"http://terrainracing.com/ios/events_json.php"];

    NSURL *terrainUrl = [NSURL URLWithString:terrainString];

    NSData  *terrainData = [NSData  dataWithContentsOfURL:terrainUrl];

    NSError *error;

    NSArray *terrainJsonArray = [NSJSONSerialization JSONObjectWithData:terrainData options:kNilOptions error:&error];

    NSLog(@"%@", terrainJsonArray);
}

user467105 · Accepted Answer · 2012-03-23 01:38:24Z

2

The picker view delegate methods are looking at the class instance variable self.terrainJsonArray (actually it's the property getter for the instance variable).

In viewDidLoad, you are declaring and logging a local variable named terrainJsonArray. This local variable has no connection to the instance variable.

You must be getting a compiler warning in viewDidLoad like "Local declaration of 'terrainJsonArray' hides instance variable".

Change this line:

NSArray *terrainJsonArray = [NSJSONSerialization JSONObjectWithData:terrainData options:kNilOptions error:&error];

to:

self.terrainJsonArray = [NSJSONSerialization JSONObjectWithData:terrainData options:kNilOptions error:&error];

answered Mar 23, 2012 at 1:38

user467105

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2 Comments

Ryne 'toast' Gray Over a year ago

thanks so much! that fixed it. this is my first app not from a tutorial so i'm still learning the differences between instance/local etc.

Ryne 'toast' Gray Over a year ago

also, sorry i cant vote the answer up, im new to the forum and not allowed yet.

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