This is the third part in the introductory series covering Robotlegs AS3 here on InsideRIA. In the first part in the series we learned what Robotlegs AS3 is and had a brief 'HelloWorld' introduction to the Robotlegs Context and Mediator classes. In the second part we explored Models. This article is going to expand on those concepts and introduce Services.
If you missed the first two parts I recommend looking at them first:
What is a Service?
The name of this website is InsideRIA. A Service is your application's link to the I in RIA. Services provide your application an API to access web services, data sources, and other applications. This could be accessing the Twitter API, your company/client's web server, the file system, or a host of other sources of data outside of your application.
A Service makes remote calls and parses the results. After the results are parsed, the service will notify the rest of the application that data is ready and/or update a Model with the results. We want external data to live as short of a life as possible within our applications. As soon as we get the results, they are converted to a format that is specific to the application domain. This might be XML, JSON, or typed Objects from an AMF source. When we are working in a 'controlled' environment, meaning the server-side mid-tier is within our control, sometimes we can avoid parsing altogether because the returned objects are already part of the application domain. In many situations we are accessing third-party servers and receiving 'foreign' data. This is what we want to parse.
Let's make something!
So with the definition behind us, lets look at how a Service functions within a Robotlegs AS3 application. This example is going to make use of the basic Twitter Search API.
The diagram above is the general overview of how our service will function. It receives a request, asks the server for some data, parses the results, and notifies the rest of the application. The requests are generally made from Mediators and Commands. In this example, we are going to keep it simple and make requests to the service from a Mediator. In the next article we will talk about how Commands are a great place to access services. Let's take a look at the finished widget and then build it from the ground up.
So it's not the next TweetDeck, but it is about as simple as it gets when accessing the Twitter API. The widget access the Twitter Search API and returns the current results for 'robotlegs.' We'll start simple, and add complexity later if we need to. Let's take a look at the pieces that go into to putting this together [...]
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