Getting Started

ChangeMachine is designed to work in similar fashion to manufacturing plant, whereby a plant is made up of many machines that perform a single function, and items (or materials) enter the machine, get processed and leave the machine.

In most cases, a machine processes an item successfully:

machine.on('process', function(item) {
        // do something with the item

        // mark the item as done
        item.done();
});

But sometimes things can go wrong:

machine.on('process', function(item) {
        try {
                // do something with the item

                // mark the item as done
                item.done();
        }
        catch (e) {
                // mark the item as failed
                item.fail({ error: e });
        }
});

Additionally, sometimes you might receive an error when something is done but not want to have to call a separate fail function. You can do this by passing an error in the options for any of the done, fail or skip methods and the status will be remapped to fail:

machine.on('process', function(item) {
        // write the item data to a file
        writeItemData(item, function(err) {
                item.done({ error: err });
        });
});

Regardless of how you flag that an item has failed, you probably want to know about it:

machine.on('fail', function(item, err) {
        console.log('got a failed item: ' + item.id);
});