Getting data from a server is a pretty common task in iOS and I found a lot of examples using AFNetworking and other libaries out there. This example is how to get JSON data from a server and serialize it into a NSDictionary so you can use it in your app using all built in functions.
Our API today will be Markit On Demand. You can check out their API docs and see everything it can do. Today we’re just going to get the last price for a certain stock.
Here is the response from the API when looking up AAPL.
So how do we get this data into iOS? First we have to make an NSURL object, then a NSData object with the content of that URL, then finally we need to deserialize that data into a NSDictionary that we can use.
NSURL *apiURL = [NSURL URLWithString:@"http://dev.markitondemand.com/Api/v2/Quote/json?symbol=AAPL"];
NSData *apiJSONData = [NSData dataWithContentsOfURL:apiURL];
NSDictionary *stockData = [NSJSONSerialization JSONObjectWithData:apiJSONData options:NSJSONReadingMutableContainers error:nil];
If you want to take user input for the searches, you can use NSString’s build in function stringWithFormat as seen here:
NSString *stockSymbol = @"AAPL";
NSURL *apiURL = [NSURL URLWithString:[NSString stringWithFormat:@"http://dev.markitondemand.com/Api/v2/Quote/json?symbol=%@", stockSymbol]];
Finally when you have your NSDictionary with info you can show that to the user with some labels on the screen.
nameLabel.text = [NSString stringWithFormat:@"Name: %@",[stockData objectForKey:@"Name"]];
priceLabel.text = [NSString stringWithFormat:@"Price: %@", [stockData objectForKey:@"LastPrice"]];