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The same simple Algorithmia API that works with Python, Java, Scala, and others, is easy for iOS programming too.
This short lesson assumes you have a basic knowledge of iOS programming: enough to write a simple single-view app using the Storyboard. (If not, start with Apple’s documentation here). To run this example, all you need is a Mac and a copy of Apple’s (free) XCode development environment.
The Algorithmia API works through simple HTTP POST commands. Fortunately, iOS already provides several powerful networking object classes that make that very easy:
- NSMutableURLRequest sets up the HTTP request with some straightforward and obvious methods, like setHTTPMethod:@“POST” to tell the server that you want to post some data.
- NSURLSession is a powerful class that lets you download the content via HTTP, including in the background or even while the application is suspended. Fortunately, the methods to control the download behavior are pretty straightforward.
- NSURLDataTask is a related class specifically for getting data via HTTP. Pass it an instance ofNSURLSession, a NSMutableURLRequest and handler that describes what to do when it receives the a response from the server.
- Finally, NSJSONSerialization is a handy class that will convert between JSON and native iOS dictionary or array types. Read Apple’s class reference documentation to see how much work this will save you!
Example: POST a string to the Algorithmia API
The best way to understand is with a simple example. Here’s a short program to send a string representation of an integer to the Algorithmia isPrime API, to find whether an input number is prime or not.
Here’s the opening screen:
Just a normal text input box (UITextEdit), a button you push to submit the text to the server, and a few labels to show what’s happening. That’s all there is to the UI, and you should be able to whip this up quickly yourself in Storyboard.
As for the guts of the app, we need to specify three things:
- The Algorithm path/uri, in this case it is ‘diego/isPrime’
- Your API key, which you can get from the Profile/Credentials page
- The right HTTP headers, as described in the API Docs – Getting Started.
That’s it! All the networking code you need to access the Algorithmia API is right there. Perhaps the most important thing to point out here is the URI format and the HTTP Headers. Whenever you’re in doubt about these details, you should browse to a random algorithm and inspect the cURL parameters given in the ‘API Usage Examples’ section.