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High in the previous lecture, he learned about messages, which is the primary method by which a note

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will pass data to another note.

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There's another way to do that as well.

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And that is done by our variables with variables.

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It's possible to pass data between notes in the same flow, but also notes across different flows.

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So I'm going to give you a few examples, a few demonstrations that use messages that use variables

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to do that.

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I want to point out that there is a very good page, a the competition page in the note read website,

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which is this one here.

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And I encourage you, of course, to have a look at this.

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It will give you a lot of details in this lecture.

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I'm going to focus on examples.

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So a central concept in note read is the context, which has got the same meaning as a context in programming

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and programming language.

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So when it comes to variables in note read, the context can be the node or a flow or global.

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So node, of course, means that you can create fireballs that are only accessible inside the node in

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particular.

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That is true for function nodes where you write small javascript flow means the context within a flow.

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OK, within a tab.

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All of the nodes inside ATAP, which is a flow, can access variables that have been created within

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this flow.

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And then for the global variables, we are talking about variables that can be accessed and can be shared

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across multiple flows to demonstrate the different kinds of variables, especially flow and global variables.

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I'm going to use my DHT 22 example flow as the starting point.

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So this is the flow that you are already familiar with from the previous lecture.

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What I'll do is I'm going to disable those debug messages and I've just actually added another debug

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node here so that I can print out the temperature and humidity to the back window.

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So if I trigger it, actually should deploy first or trigger this flow.

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And this is what you get.

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The idea here is that instead of printing out the temperature and humidity, connecting the debug nodes

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directly to the DHT 22 node, what I'll do is I'm going to store these two values in flow and in global

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variables and then access them by triggering a different part of the flow or by getting them in a totally

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different flow and presenting them into the deep window.

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Again, I'm going to start with local flow variables.

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There's a couple of different ways to work with variables, whether they are global or flow, and that

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is by creating them and accessing them programmatically inside a function node or by using one of the

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compatible nodes to first I'm going to work with a compatible node.

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And then I'm also going to show you the second way of doing that through functions, which is obviously

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a lot more flexible.

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So before we can read a flow variable, we need to create it.

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And to do that will use the change node and grab a node and place it up here and then connect Mattituck

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22 node to the change node inside the change node.

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I'm going to create two rooms I'm going to set.

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A flu.

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A variable called.

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Temperature.

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To whatever message DOD payload contains, as you know, payload is the variable that contains the temperature,

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and then I'm going to do the same thing for humidity.

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I'm going to set the humidity flow.

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To message dot.

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Humidity.

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And that's it, I might put another debug message here so that.

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Let's see, I'm going to add another message and set the payload that will come out of the change node

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to say something like variables set.

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All right, so then that output will go into the debug node here and I'm going to give it a name, Farabaugh

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Verbose set confirmation.

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All right.

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So what I've got now is that the G20 to take a measurement, it will pass the data onto the change through

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the change, is going to set the Flotard temperature and Flotard humidity variables.

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And then it's also going to set the message payload vulnerable to this string so that in the next note,

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the debug note, I'm just going to print out that message that the variables have been set and confirmation.

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Now, let's see how that works so far.

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I'm going to deploy and then trigger this flu and you can see that virus said.

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So we want to be able to read them.

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Right.

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So let's go ahead and do the reading of those flu variables to do that.

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I'm going to use an inject note and in that inject note, I am going to read a flu virus first the temperature.

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I'll give it a name, read SLU.

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Temperature, I read, read low temperature variable underneath the second topic.

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Done and then printed out to the back window, I just say show temperature, actually low temperature

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Vudu.

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Like that, and I'll do the same thing for humidity, so I just copy and paste.

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The original note and change this to humidity, and now I want to get the humidity flow variable, variable.

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Like that.

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I can actually connect this node to the same debug node if I want, and I can just say show flow values.

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Like this sense for both of these inject notes, the message is printed or is stored inside the message

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payload vulnerable and that should work.

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I'm going to test that.

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And if it doesn't work, I'm going to split up into two debug nodes.

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All right.

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So let's deploy that and clean up.

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And first, we want to get a reading from the data twenty to sensor.

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So there's the reading.

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And next, I want to read the flow variables first, the temperature one.

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There it is.

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And then second, the slow bearable for humidity and there it is so they can see these two sub flows

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are not connected through wires or no messages are being passed around directly, but they do communicate

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via flow variables.

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And to stop flooding the debug window with messages every 10 seconds from the day to I'm just going

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to disable those to debug notes.

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All right.

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One thing to notice here is that every time that the teacher, 22, is triggered and then the flow variables

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are changed or updated, I get confirmation that variables have been set from this dybbuk.

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Now, let's do the same thing.

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But past those variables over to a second flow in a different tab.

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So to do that, we need to use global variables.

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So let's go ahead and do that first.

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I'm going to go back into my change mode and add another two sets.

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So the first one is going to go to a global temperature.

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Vargas is going to set the global temperature variable and of course, we want to grab the value from

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message payload for this.

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And the second one, you can probably guess it will do the same thing.

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But for global.

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So I'm just going to copy humidity and then.

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The value for the global humidity variable will come from.

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And g humidity, so the message object to humidity and done, then I'm going to copy these three modes.

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So command to see, to copy, I'm going to place them in my new flow, in the verbose flow, and I'm

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just going to change.

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Flow to global.

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And again, flew to grovel for the payload, and that should be enough.

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I'm just going to change this to show global values, global values and.

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Deploy.

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All right.

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Let's trigger the DHT 22 sensor variables set and then go into the variables and context example flow

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and take a reading.

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So the second one, the humidity works, the first one does not, why's that global temperature so much

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of miswired something?

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Let's go back in my rules and let's see.

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Humidity did not work.

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So this is interesting, so I'll just show you again the problem here.

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So let's have a look at the global variables.

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I'm going to trigger the temperature variable first.

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Hmm.

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And it's giving me the variable set, which is not temperature.

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I'm going to look into this in a moment.

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And what about the humidity?

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Yes.

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And humidity works.

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So there's a little bug here.

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Let's try and figure out why this is happening.

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So I'm going to go back to my DHT.

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Twenty two example Fluked and then inside the change node and let's see.

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I think the problem is right here, as you can see, that in this step, in this rule, I should say,

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we said the payload to be viable set just a string of text, and then in the next one, setting temperature

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to be the payload, which is what I've set of reset to be the string, Viterbo said.

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So this is where the bug is to fix it.

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I to move the payload set to the bottom of the list of rules so that the global temperature variable

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is set to meet such payload before message payload is changed.

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All right.

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So that you do it.

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Can we deploy again?

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And.

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The flow still still working.

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I'm going to trigger it, actually, just to be sure.

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OK, and then going to verbals and check.

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Temperature in this twenty two degrees and the humidity.

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All right, so that works.

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So I can see that we can use global variables set by this change room so that these variables can be

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accessed across multiple flows.

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Now, one thing that I also want to do is to have the ability to clear those variables.

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So I'm going to show you how to do that in a moment, again, using the change rule.

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But before we do that and show you how to reset or how to to clear the flow or global variables, I'm

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going to show you how to set them and treat them using JavaScript inside a function node.

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So let's pick a function going to place set up here and connect it to the to the twenty two node like

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this and then in it.

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I'm going to just do a bit of copy paste to save a bit of typing like this, so programmatically you

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can set a flow variable by using Flotard set first parameter to give you a variable, a name, and then

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the second parameter, whatever value you want to store in it.

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In this case, I'm going to store the value stored in message humidity inside the humidity, flue variable

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and the value stored in a mosquito payload inside the temperature through variable.

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It's going to give this function a name and that's about it.

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I don't really care what comes out of it because I am not going to connect anything to this particular

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function node.

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All right.

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So this is how you can set a variable.

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And now let's read those two local or flow variables using a function node and a little bit of JavaScript

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inside it.

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So here's my function node.

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I'm going to go in and copy a little bit of code that does the reading.

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So it looks like this very simple.

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I'm using slow dot get and pass on the name of the flow Viterbo that I want to get the value off and

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whatever comes back will store it in the humidity.

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Local actually node variable and doing the same thing for the temperature variable.

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All right.

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Now I would like to get those two variables sent out to debug nodes and I want to have two different

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debug nodes connected to this function.

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So I'm going to create a an array.

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They contained two small Jason documents inside, so each one has got its own payload, first one has

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got the temperature of the second one, the humidity.

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You've seen this notation before.

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So this is going to have to outputs.

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And before I forget, I will give this function or a name.

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All right, so here is our function and we need to Depok notes.

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Of course, I could simply connect those two outputs to this debug note, but just keep things tidy

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and separate for now.

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All right.

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So the first one is going to be the temperature.

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It's going to float temperature.

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And the second one is going to be the slow.

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Humidity.

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And lost, I need some way to trigger this function, so again, I'll use and inject Nood.

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All right, I just send that a number does really matter what it is, whatever it is, it will trigger

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the funky mood chocolate trigger.

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All right, to deploy, clean up and first trigger the DG to sensor variables is set and then let's

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trigger the function to rip them out that you.

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OK, now the last thing to do is to expand our function here so that it also sets global variable so

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that we can read them from a separate flow, you can probably figure out how to do that is very easy.

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So first, I'm just going to duplicate these two lines and instead of flow will say global.

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And done, then I'm going to copy this set of notes and pasted in my separate smile like that, and

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all I've got to do to make this work is to change flow.

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To global.

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And that you work, so let's give this a go and deploy and clean, the robots are already in memory,

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so I'm going to click on Trigger.

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These are the flu viruses that these are the global variables now coming through the debug window.

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Awesome.

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So now you know how to use both global and flu variables.

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One thing I should mention is that these variables and the values are stored in memory.

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When you deploy the flu or even if you go through full deployment or even a restarting of the Flo's,

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those variables still remain in memory and they will only change if you do so via the function or change

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node.

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Now, if you want to reset or even delete these variables in order to start from a clean slate, that's

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particularly important when you are debugging and you're testing a new flu, then you have to do that

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manually again using change mode.

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So let's do that now, can take a change node and then go in and say that this is going to be a node

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that cleans or cleans or variables and just choose the delete rule.

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So you want to delete.

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Humidity.

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At the flow level.

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Delate.

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Actually makes the global humidity and then another to delete.

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Flo.

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Temperature.

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And again, the late.

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Global temperature.

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And I want to also set the notification, so I'm going to use a debug.

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Note to indicate to me that fireboats had been deleted.

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All right, then let's have our debug window to confirm deletion.

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So I'm going to call it delete confirmation, and again, I need the trigger, so I'm going to copy

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the trigger note and connected to the change node.

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All right, so I'm going to deploy and first, let's see what is inside our flow variables.

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So I'm going to trigger flood variables.

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And you can see that they do have defined values.

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Then I'm going to trigger the cleaner.

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So trigger plenel variables and variables deleted.

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Then I'm going to trigger again the arete flow variables.

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So now let's have a look at the flow variables.

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You can see that they are not defined.

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I just noticed.

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Need to make a little correction here.

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So this should be get not set.

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Right.

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OK, now if I want to reset the global flow variables, I just need to trigger this sub flow.

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So that's a value stored in those variables and then I can check them out again and you can see that

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they're now set.

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Same thing happens, of course, at the global context.

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So right now, the global context has got values.

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If I clean those variables again, because in the meantime, they would sit so clean them and then test

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them, they could see that different.

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OK, so with this, you now know everything you need to know to be able to work with flow and global

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variables in the context of this project.

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So in the remaining lectures in this section, I'm going to demonstrate the use of several other notes

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from the left toolbar that will be using in this project.