Question

I’m having a bit of trouble figuring out why this code is running slow. What I’m doing below is getting JSON data from yahoo finance for 4 companies. From the JSON data I’m simply extracting the names of the 4 companies. However as I NSLog the names of the 4 companies it takes almost 2 full seconds to do so! Is their something in the code that I’m doing wrong? how can I get the code to run faster?

for (int i=0; i<4; i++) {
    //download JSON data
    NSData* data = [NSData dataWithContentsOfURL: 
                    [NSURL URLWithString:@"http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.quotes%20where%20symbol%20in%20(%22AAPL%22,%22GOOG%22,%22GE%22,%22MCD%22)%0A%09%09&env=http%3A%2F%2Fdatatables.org%2Falltables.env&format=json"]];

    //parse out the json data
    NSError* error;
    NSDictionary* json = [NSJSONSerialization 
                          JSONObjectWithData:data //1

                          options:kNilOptions 
                          error:&error];

    //Get the relavent data from JSON
    NSString* companyName = [[[[[json objectForKey:@"query"] objectForKey:@"results"] objectForKey:@"quote"] objectAtIndex:i] objectForKey:@"Name"] ;

    NSLog(@"company name is %@", companyName);
}

Answer 1

As Richard said, don’t download the file 4 times. As a first iteration try this:

   //download JSON data
    NSData* data = [NSData dataWithContentsOfURL: 
                    [NSURL URLWithString:@"http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.quotes%20where%20symbol%20in%20(%22AAPL%22,%22GOOG%22,%22GE%22,%22MCD%22)%0A%09%09&env=http%3A%2F%2Fdatatables.org%2Falltables.env&format=json"]];

    //parse out the json data
    NSError* error;
    NSDictionary* json = [NSJSONSerialization 
                          JSONObjectWithData:data //1

                          options:kNilOptions 
                          error:&error];

for (int i=0; i<4; i++) {

    //Get the relavent data from JSON
    NSString* companyName = [[[[[json objectForKey:@"query"] objectForKey:@"results"] objectForKey:@"quote"] objectAtIndex:i] objectForKey:@"Name"] ;

    NSLog(@"company name is %@", companyName);
}