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In the previous lecture, he learned about some flows, some fluids provide an easy way to organize

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your flows so that you can reuse parts.

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And in this lecture, I wanted to take another step and take another look into such flows and show you

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three different ways by which you can exchange data between a flow and a flow in this lecture.

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I have taken the example from the previous lecture and extended it in order to do my three demonstrations.

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I'm going to show you how to exchange data between a flow and its flow.

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First, by using flow variables.

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What I want to show you how to use global variables.

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And finally, how to return one or more values from my flow.

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Lack of court in this case a right here.

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But let's start from the beginning.

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Obviously, the easiest way to exchange data between a flow and other flows as well as between a flow

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and a sub flow, is to use our global variable.

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So in this example, I've got my trigger, as you see in the previous lecture of editor, a little delay

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here because there's a few things that are happening as well that I want to make sure that the timings

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are correct.

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But after 1/2 we go into the DHT 22 sub flow, which we can see here.

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This node will go to the sensor and grab the temperature and humidity and print them into the debug

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window, but also use these two change nodes to set a global temperature variable and a global humidity

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variable, as you can see here.

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So just use the global context from the dropdown here.

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Back in our main flow.

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We wait for 5 seconds and then I use the change node to grab the values stored in the global temperature

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and global humidity variables and then set them into the message payload and message humidity variable

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should then those can then be printed into the output.

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Just like that.

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So let's run it.

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I'm going to trigger the flow.

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Give it a bit of time, especially for the 5 seconds, so that we can grab the global temperatures.

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And here they are.

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So humidity global and temperature global.

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And they say values.

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Those values, again, were set inside the flow, using these to know which is to change routes.

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So this is easy again.

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You can use the same technique to communicate values across flows in a project.

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If you want to be a little bit more precise about who has access or which flow, as you'd say, has

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access to a particular value, then global via voice is a bit of an overkill.

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It's like using a global variable in a regular program.

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Best to be avoided and best to have a little bit more control set in.

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So another way you can go about doing this is to use a flow variable.

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A parent variable can share its flow variables with a sub flow and I'll show you how.

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So here we've got the trigger.

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I've set the trigger so that it will store the timestamp into the message payload attribute.

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So once I click on this button to trigger the trigger node, I will go into the change node.

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And in the change node I take the payload time and date stamp and store it in a flow context variable

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called trigger time.

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So flow don't trigger time.

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Then wait for a second and go into the sub flow and inside the sub flow.

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Right here in this function I have a little bit of JavaScript code which uses the flow to get API call.

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And what I want to do is to get the value stored in the flow trigger time or flow don't actually get

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time.

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But because this flow trigger time value is stored in a flow variable that was created by the parent

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of these sub flow, I need to prepare a dollar sign parent to the name of the variable that I'm accessing.

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So.

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So the result is that I'm using float to get and then in parentheses it's dollar sign parent which gives

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me access to the flu virus of the parent dot trigger time, which is a name of the variable that I want

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to access.

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I take the content of this.

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Variable in my JavaScript program and store it in the payload of the message and then return that message

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once the triggered time that is stored in the parent's flow variable is captured by my JavaScript,

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it printed out into the debug window by this debug node and the name of this node is Print Flow Timestamp.

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That's the one that I'm going to look for in a moment.

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When I trigger the flow switch, go back to the main flow and trigger it.

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And.

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Here is the print flow timestamp output, which is this number here, which is identical to the timestamp

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variable that came out of the trigger mode.

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Okay.

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So this is the second way by which you can exchange data between a flow and any of its sub flows.

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I also wanted to show you a way by which you can return one or more values from a subfloor.

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You can see it here.

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I've got my DHT 22 subfloor, and you can see that there are two connectors coming out of it that I

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then connect to debug notes.

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The way you can do this is first in your sub flow to create as many outputs as you need.

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So in this case I've got two outputs.

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I can add more and you can see that output nodes appear.

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Or can delete them and then you need to provide some value going into this output set will be then exposed

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to the main flow.

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In my case, I used a function in this function of got a little bit of JavaScript.

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This JavaScript creates the humidity and temperature variables in the humidity variable.

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I store message the payload attribute temperature Walsh store message dot humidity attribute.

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And then for my return statement, I've got an array and in an array of call it means JSON statement

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where I've got two payloads.

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One payload has the value of temperature, the second payload, the value of humidity.

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And from there I've got my two output connectors which are connect to the output nodes for my stuff

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flew.

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These will then come out into the main flow where I can connect them to other nodes.

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In this case, two other debug nodes for this trigger.

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This flow one more time and see what comes out of these two specific nodes.

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It's going to take 1/2 to show supply.

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Temperature is right here and then the low flow humidity is right here.

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Returned by the flew.

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And to recap.

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There are a few ways by which you can exchange data between a flow and sub flows, and in this lecture

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I showed you three of those ways.

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It can use flow variables which are accessible from a sub flow.

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By using the parent preprint in the name of the flow variable that you want to access, then you can

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use global variables which allow data exchange across any flow or sub flows in a project.

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And finally, you've learned how you can return one or more values from a sub flow using the function.