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And so let's play with that a little bit.
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So first let's copy this, that way you can keep it.
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So let's clear all of this and then play with mounting a little bit.
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And so in your next project what you're going to do is you're
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going to be implementing what's called a Pomodoro timer.
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And so for those of you who are aware of what those are--
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basically what it is is a timer that allows you
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to switch between two amounts of time.
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And so there's this thing called the Pomodoro Technique which
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is used for studying where you study or work very hard for some amount of time
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and then you take a short break.
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And then you work hard for some short amount of time
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and then you take a short break.
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And so what you're going to be creating in your next project
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is actually a timer that allows you to do that.
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It will automatically track for you however long you want to work.
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And it will also allow you to set some time
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that you want to take a break in between those working blocks.
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And it will do that.
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So when you start the timer it will count down until you're done working.
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It will let you know, hey time for a break.
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Then it will switch over to that break timer,
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run down until that ends up and says, oh now it's time to work,
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and it will cycle through that.
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And so in order to do that, you might need
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to know how to work things like timers.
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And so these methods may be a chance for you to set up those timers.
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And so let's go ahead and do an example doing that.
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So first let's get rid of all of this stuff.
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So in this example we no longer need TODOs.
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And in our render lets actually just have some count.
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Those have a View.
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And inside here let's have some text.
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And that text is just going to show some count.
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And let's initialize that count to 0.
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So, as soon as I get rid of all this, we have a very simple app and all it does
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is show a count of 0.
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You see it up in this left hand corner here.
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And let's go ahead and actually center this.
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So let's do styles, and let's create a new style sheet.
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Let's call this app container and whatever we want to do in here.
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So let's have it grow as much as we can.
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Let's have it center its items.
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And let's have it align its items the other direction as well.
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And down here let's actually pass this in as styles.appcontainer.
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So now we see this number 0 is very small.
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Let's go ahead and make it a little bit bigger.
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And so let's have count and let's give it a big font
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size of like 48 or something.
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So now-- style--
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we have a big number and all it does is 0.
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And so how are we going to get it to count?
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Well presumably we should be setting our state
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and just have that state increase.
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And so if we want to repeat something what might we use to achieve that?
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So do something at some given interval.
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We can actually use that set interval.
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And so let's first implement this count.
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So let's have this thing called increment.
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Is this too small?
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Let's have this thing called ink.
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And what that does is it does this.setstate, takes a previous state
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and returns the count to be 1 greater than the previous state.
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And so now we've implemented this thing called increment where we
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take the states count and increment it.
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And so how might we get this increment call to happen every once in a while?
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Well presumably we should use a thing called
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set interval, which we'll call a function every n milliseconds.
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But how are we going to get that to happen?
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Well we should do this after the component finishes mounting.
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We should set up some sort of timer.
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And so how do we know or how do we get a function
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to execute after components finish mounting?
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That's actually where this lifecycle method comes in.
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And so there's this lifecycle method called
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componentDidMount which automatically gets
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run for after the component mounts.
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And so we can actually set up our timer tap in there.
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And so we can do componentDidMount and inside of it we can do setInterval
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and that's called this.Increment every second.
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And so there's going to be a small bug here.
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Does anybody know what the bug is?
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So every 1,000 milliseconds this thing called this.Increment is getting
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called.
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And this.Increment is invoking this.Setstate.
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Does anybody see how that might be a problem?
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I'll give you a hint.
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It has something to do with this.
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And so when this gets executed this might not mean what this is here.
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And so this is a common bug in React.
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Oftentimes, when you say this here, what it means
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lexically is not necessarily what it means
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when it actually eventually gets run.
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And so how did we go about fixing this bug in previous lectures?
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We have to somehow get this to be bound to what we want it to be.
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And in case we want it to be bound lexically.
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So a few different ways to do that.
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One way was creating a new function here in line that does this.
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And I'm actually not sure that that works in this example
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because this isn't necessarily set here.
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