UIPickerView cannot display JSON array data

Question

This is my first time doing an iOS app, so I may not know some stuff that may seem easy. Please be patient with me =)

Basically, I need to fill up my UIPickerView with data from my JSON. I have successfully parsed my JSON data and pulled out what I need and placed them into an NSMutableArray. When I first tried to do the UIPickerView, I used hardcoded array, and everything was working fine. Now, when I try to replace the hardcoded array with my JSON array, I keep getting a null JSON array. The way it works, it seems that the UIPickerView tried to pull everything out before my JSON array is filled.

I have tried reloading the UIPickerView as suggested elsewhere on this site, and it also isn't working.

The following are parts of my code:

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    dispatch_async(randomiserBgQ, ^{
        NSData* data = [NSData dataWithContentsOfURL:randomiserCatURL];
        [self performSelectorOnMainThread:@selector(fetchedData:) withObject:data waitUntilDone:YES];
    });
}



- (void)fetchedData:(NSData *)responseData{
        NSError* error;
        NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];

        NSArray* randomiserCat = [json objectForKey:@"categories"];
        self.randCatSel =[[NSMutableArray alloc] init];

        NSLog(@"categories: %@", randomiserCat);

      for (int i = 0; i < [randomiserCat count]; i++) {
            NSDictionary *dict = [randomiserCat objectAtIndex:i];
            NSString* parent = [dict objectForKey:@"name"];
            [self.randCatSel addObject:parent];
            NSArray* childrenArray = [dict objectForKey:@"children"];

            for (int i = 0; i < [childrenArray count]; i++) {
                NSDictionary* dict = [childrenArray objectAtIndex:i];
                NSString* children = [dict objectForKey:@"name"];
                [self.randCatSel addObject:children];
                NSArray* grandchildrenArray = [dict objectForKey:@"grandchildren"];

                for (int i = 0; i < [grandchildrenArray count]; i++) {
                    NSDictionary* dict = [grandchildrenArray objectAtIndex:i];
                    NSString* grandchildren = [dict objectForKey:@"name"];
                    [self.randCatSel addObject:grandchildren];
                }
            }
        }
}

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


- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent: (NSInteger)component
{
    return [self.randCatSel count];    
}

-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row   forComponent:(NSInteger)component
{
    return [self.randCatSel objectAtIndex:row];
}

As you can see, the way I tried to parse my JSON data, I used such a long method as I have a few levels of arrays in the JSON data. If there is a faster method (like foreach in PHP), please point me in the right direction as well.

So far, my UIPickerView is getting a empty randCatSel array (I presume it is loading it before it is filled).

You can use [pickerViewObj reloadAllComponents]; after json parsing. — Bhumeshwer katre
– Bhumeshwer katre, Commented Dec 23, 2013 at 4:56
You can use for(NSDictionary *dic in randomiserCat) just like foreach — mak
– mak, Commented Dec 23, 2013 at 4:57
Avoid displaying the picker until you obtain the data. And then reload the picker. — mak
– mak, Commented Dec 23, 2013 at 4:59
[self.thePickerView reloadAllComponents];add this line in this method- (void)fetchedData:(NSData *)responseData after end of closing bresses of for loop.this problem is occuring due to you are not loading your pickerview with new data of array — kamalesh kumar yadav
– kamalesh kumar yadav, Commented Dec 23, 2013 at 5:13

hpp · Accepted Answer · 2013-12-23 05:38:11Z

hi please try this,

- (void)fetchedData:(NSData *)responseData
{
        NSError* error;
        NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];

        NSArray* randomiserCat = [json objectForKey:@"categories"];
        self.randCatSel =[[NSMutableArray alloc] init];

        NSLog(@"categories: %@", randomiserCat);

      for (int i = 0; i < [randomiserCat count]; i++) {
            NSDictionary *dict = [randomiserCat objectAtIndex:i];
            NSString* parent = [dict objectForKey:@"name"];
            [self.randCatSel addObject:parent];
            NSArray* childrenArray = [dict objectForKey:@"children"];

            for (int i = 0; i < [childrenArray count]; i++) {
                NSDictionary* dict = [childrenArray objectAtIndex:i];
                NSString* children = [dict objectForKey:@"name"];
                [self.randCatSel addObject:children];
                NSArray* grandchildrenArray = [dict objectForKey:@"grandchildren"];

                for (int i = 0; i < [grandchildrenArray count]; i++) {
                    NSDictionary* dict = [grandchildrenArray objectAtIndex:i];
                    NSString* grandchildren = [dict objectForKey:@"name"];
                    [self.randCatSel addObject:grandchildren];
                }
            }
        }
    packerView=[[UIPickerView alloc] initWithFrame:CGRectMake(0, 280, 320, 200)];
packerView.delegate=self;
packerView.dataSource=self;
[self.view addSubview:packerView];

}
//add the picker view delegate and datasource in .h file. and set the frame as per your requirement.

hope this will help you.

I didn't try your answer, but I assume it's correct, as I've seen the last 3 lines of the code before. However, reloadAllComponents can save you some lines of codes =)

SilverHood · Accepted Answer · 2013-12-23 06:28:27Z

1

As pointed out by the wonderful people here, all I had to do was to reload the UIPickerView in my fetchedData method. I previously put it in viewDidLoad =/

[pickerViewObj reloadAllComponents];

Where pickerViewObj is your own UIPickerView.

answered Dec 23, 2013 at 6:28

SilverHood

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