在目标c数组上解析Webservice的JSON

Question

I'm developing an iphone app and I have a JSON from web service as below:

[
    {
        "0":"test_w",
        "assignment_title":"test_w",
        "1":"2011-11-02 04:02:00",
        "assignment_publishing_datetime":"2011-11-02 04:02:00",
        "2":"2011-11-02 01:53:00",
        "assignment_due_datetime":"2011-11-02 01:53:00",
        "3":"course_math.png",
        "course_icon":"course_math.png",
        "4":null,
        "submission_id":null
    },
    {
        "0":"\u062a\u0637\u0628\u064a\u0642 \u0631\u0642\u0645 3",
        "assignment_title":"\u062a\u0637\u0628\u064a\u0642 \u0631\u0642\u0645 3",
        "1":"2011-08-08 00:00:00",
        "assignment_publishing_datetime":"2011-08-08 00:00:00",
        "2":"2011-08-25 00:00:00",
        "assignment_due_datetime":"2011-08-25 00:00:00",
        "3":"course_math.png",
        "course_icon":"course_math.png",
        "4":null,
        "submission_id":null
    }
]

also I have a tableview and I need to parser assignment_title only on the tableview cells , also I'm using SBJSON library.

so what is the best way to extract assignment_title and put them on cells?

Answer 1

I find the solution from your answers as below:

I created a method with 2 parameters (json_path , field [that i need to show in tableview cell])

- (NSMutableArray*)JSONPath:(NSString *)path JSONField:(NSString *)field{
    SBJSON *parser = [[SBJSON alloc] init];
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:path]];
    // Perform request and get JSON back as a NSData object
    NSData *response = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];

    // Get JSON as a NSString from NSData response
    NSString *json_string = [[NSString alloc] initWithData:response encoding:NSUTF8StringEncoding];

    NSArray *statuses = [parser objectWithString:json_string error:nil];

    NSMutableArray * tempMutArray = [[[NSMutableArray alloc] init] autorelease];
    int i;
    for (i=0; i<[statuses count]; i++) {
            [tempMutArray addObject:[[statuses objectAtIndex:i] objectForKey:field]];
    }

    return [tempMutArray copy];

}

after that i call it in cell as following:

//in viewDidLoad
NSArray * homework = [self JSONPath:@"http://....." JSONField:@"assignment_title"];

//In cellForRowAtIndexPath
cell.textLabel.text = [homework objectAtIndex:indexPath.row];

Thanks to all

Answer 2

If you are doing it through NSJSONSerialization you can get array of assignment_title using this simple method ;)

NSError *error = nil;
NSData *jsonData = [NSData dataWithContentsOfURL:apiURL]; 
id jsonObjectFound = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&error];
NSArray* assignmentTitles = [jsonObjectFound valueForKey:@"assignment_title"];

Answer 3

If performance matters, you might consider using an ASIHTTPRequest to fetch the json asynchronously, then inside the requestFinished: you might do something like:

- (void)requestFinished:(ASIHTTPRequest *)request
{
   // Use when fetching text data
   NSString *responseString = [request responseString];

   //assuming you created a property instance variable NSArray *myArrAssignmentTitles
   NSArray *tempArray = [responseString JSONValue];
   //making an array of assignment_title
   NSMutableArray *tempMutArray = [[NSMutableArray alloc] init];
   int i;
   for(i = 0;i < [tempArray count];i++){
       [tempMutArray addObject:[[tempArray objectAtIndex:i] objectForKey:@"assignment_title"]];
   }
   //assign the data to the instance variable NSArray *myArrAssignmentTitles
   self.myArrAssignmentTitles = tempMutArray;
   //release tempMutArray since the instance variable has it
   [tempMutArray release];

   //call the reload table
   [self.tableView reloadData];//i think this is how to reload the table
}

- (void)requestFailed:(ASIHTTPRequest *)request
{
    NSError *error = [request error];
}

So, your myArrAssignmentTitles has all the values assignment_title from json all you do is just apply the array data for the cell eg

  cell.textLabel.text = [self.myArrAssignmentTitles objectAtIndex:indexPath.row];

its a long code sorry about that. But, thats works for me xD; it fetches the json asynchronously after that it creates an array of assignment_title hopes it helps.