Talking to JSON

Isn't it interesting to do so?. And i love the way it is. In the following steps i will explain you the steps reading json file.

my sample json file is here sample.json

{"books":

[

     { 

     "name" : "A Bend in the river", 

     "author" : "V.S. Naipaul", 

     "id" : "01" , 

      "coverurl" :"http://myiosapps.comuf.com/mySampleProjects/jsonTutorial/1.jpeg"

      },

     { 

     "name" : "Baburnama", 

     "author" : "Babur", 

     "id" : "02" , 

      "coverurl":"http://myiosapps.comuf.com/mySampleProjects/jsonTutorial/2.jpeg"

      },

     { 

     "name" : "The secret", 

     "author" : "Acharya Rajneesh", 

     "id" : "03" , 

      "coverurl" :"http://myiosapps.comuf.com/mySampleProjects/jsonTutorial/3.jpeg"

      },

{ 

     "name" : "Bermuda Triangle", 

     "author" : "Charles Berlitz", 

     "id" : "04" , 

      "coverurl" :"http://myiosapps.comuf.com/mySampleProjects/jsonTutorial/4.jpeg"

      },

{ 

     "name" : "Eye of the Storm", 

     "author" : "Patrick White", 

     "id" : "05" , 

      "coverurl" :"http://myiosapps.comuf.com/mySampleProjects/jsonTutorial/5.jpeg"

      }

  ]

}
Step 1: First thing,make sure you have the json library,if not get it from here JSON. and drag all the classes into your project.

Step 2: In the header just include the JSON.h.Now lets get into the coding part.

Step 3: In the viewdidload,lets download the sample.json file,which is kept in the server

NSData* tmpData = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"Ur json file url goes here"]];

    

    NSString* cacheDir = CacheDirectory;

    NSString* cachePath = [cacheDir stringByAppendingPathComponent:@"sample.json"];

    

    if (!tmpData){

        // attempt to get the data from the cache

        tmpData = [NSData dataWithContentsOfFile:cachePath];

    }

     

    [tmpData writeToFile:cachePath atomically:YES];

    NSString *jsonString = [[NSString alloc] initWithData:tmpData encoding:NSASCIIStringEncoding];

    NSDictionary *results = [jsonString JSONValue];

    NSArray * json_issues = [NSArray arrayWithArray: [results objectForKey:@"books"]];

    

    books = [[NSArray alloc] initWithArray:json_issues];

books has all values retrieved from json file.Now thats done,all we need to do is,just need to extract value for each key element from the dictionary object.

-(NSDictionary *)bookAtIndex:(NSInteger)index {

    return [books objectAtIndex:index];

}

-(NSString *)authorNameAtIndex:(NSInteger)index {

    return [[self bookAtIndex:index] objectForKey:@"name"];

}

-(NSString *)bookUrlAtIndex:(NSInteger)index {

    return [[self bookAtIndex:index] objectForKey:@"coverurl"];

}

-(NSString *)bookNameAtIndex:(NSInteger)index {

    return [[self bookAtIndex:index] objectForKey:@"author"];

}

Step 4: Now passing those strings to UITableView cell is not a big deal.Note that you need include UITableViewDataSource and UITableViewDelegates.

- (UITableViewCell *)tableView:(UITableView *)tableView2 cellForRowAtIndexPath:(NSIndexPath *)indexPath

{

    static NSString *CellIdentifier = @"bookCell";

    

    UITableViewCell *cell = [tableView2 dequeueReusableCellWithIdentifier:CellIdentifier];

    if (cell == nil) {

        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellSelectionStyleNone reuseIdentifier:CellIdentifier];

    }

    //cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;

    NSURL *url=[NSURL URLWithString:[self bookUrlAtIndex:indexPath.row]];

  
 //Need to include ImageDownloader class

    ImageDownloader *imageView = [[ImageDownloader alloc] initWithFrame:CGRectMake(10, 5,120, 100)];

    //imageView.contentMode = UIViewContentModeScaleAspectFill;

    imageView.clipsToBounds = YES;

    imageView.tag = IMAGE_VIEW_TAG;

   

   [[ImageLoader sharedLoader] cancelLoadingURL:imageView.imageURL];

    

    //load the image

    imageView.imageURL = url;

     [cell addSubview:imageView];

    UILabel *authorLabel=[[UILabel alloc]initWithFrame:CGRectMake(140, 30, 200, 20)];

    authorLabel.text=[self authorNameAtIndex:indexPath.row];

    authorLabel.textColor=[UIColor blackColor];

    authorLabel.textAlignment=NSTextAlignmentLeft;

    

    [cell addSubview:authorLabel];

    UILabel *bookLabel=[[UILabel alloc]initWithFrame:CGRectMake(140, 60, 200, 20)];

    bookLabel.text=[self bookNameAtIndex:indexPath.row];

    bookLabel.textColor=[UIColor blackColor];

    bookLabel.textAlignment= NSTextAlignmentLeft;

    bookLabel.font=[UIFont fontWithName:@"Helvetica" size:12];

    [cell addSubview:bookLabel];

    return cell;

}

Well this is it about reading a simple JSON file. Hope it helps you.You can download the source code here .