This video illustrates the use of the Flow tooling to build an RSS feed that is an alphabetically sorted combination of two other feeds. This video shows development taking place in real time. We build and deploy a useful application in just three minutes, emphasizing how productive a Zero developer can be.

Video Two: RSS Aggregation

Creating a simple flow: RSS Aggregation. This video demonstrates the use of the graphical tooling to build the first "Feed" sample provided in the zero.assemble.flow example project.

The flow starts with a receiveGet activity. The 'url' field specifies the final part of the URL required to invoke this flow. Once assembled, the flow's behaviour will be to aggregate and sort two RSS feeds into a single new feed. The two feeds in question are taken from the BBC and Yahoo! news services. We use GET activities to obtain each of the two input feeds. Each task requires a name and a target URL. Because they have no input wires, both activities will start immediately after rssRcv is triggered - which is what we want.

We now use the two custom activites shipped with the zero assemble flow Example project. We first use the 'aggregate' activity to combine the two feeds. Here we specify that <aggregate> will run once both GET tasks have completed, taking their outputs as its inputs. Next we use a 'sort' activity to sort the feed elements into descending order, wiring up its single <input> in the same manner.

The flow was started with a receiveGET activity. We need a matching replyGET to return the content to the requestor. Note that the 'url' field in the receive and replyGET activities must be the same.

Now the flow is complete. We save it to the eclipse project that we started earlier. 'flow name' specifies the name of the process, and 'location' the directory underneath 'public' in which the file, called index.flow will be created. Since this is a new flow, we can invoke it immediately. We expect to see a single RSS feed containing sorted content from the BBC and Yahoo! news services. Which indeed we do. That's it! Thank you for watching.

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