Flow Parameters are a special kind of temporary “variables” that exist within the flow signal itself and only for the scope/life of that flow. In practice, we can tell the flow to carry data as it moves forward from node to node and later on read that data back. We can write and read flow parameters using the ‘Write Flow Param’ and ‘Read Flow Param’ nodes respectively.

In the following example, within each iteration of the For Loop node, we write a flow param named “index” to be the index of the iteration and then a Wait node is called which in turn queues the calls. Each dequeued call then reads the “index” flow param we previously set which is finally logged.

Flow parameters can be very useful, especially when working with latent nodes as in the example above.