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Chaining Functions with andThen5:41 with Craig Dennis
Let's make use of the ability to chain methods together.
[MUSIC] 0:00 Okay, so you just started a new job at a startup called composure. 0:04 And the concept here is we keep our cool, it doesn't go away no fear of missing out, 0:08 we keep our cool. 0:12 So the project is like this, 0:14 there's a bunch of fields that users can fill things out on their profile, right? 0:16 And we started to allow HTML. 0:19 We said it was a bad idea, nobody really listened, but you know it's a bad idea. 0:22 It started to look a lot like My Space here. 0:26 The users love it, and it's moving all over the place though like 0:28 almost every single field has this concept of they can write their own HTML. 0:31 Not very cool. 0:36 So for an example, here's what happened. 0:37 So, we have some HTML here and 0:38 what we've noticed is that people like to use the strong tag a lot. 0:41 So what we've done is we've basically just removed it. 0:44 So I'm gonna go ahead and give this thing a run so that you can see what happens. 0:46 So what happens, if we've gone through this little utility here, 0:50 this a bold cleaner means some third party libraries this is a grandle project. 0:54 So I've been using some third party libraries adjacent for this one. 0:58 And basically, we get rid of the strong tags, so see it's not down here. 1:02 See allows you to over promote. 1:05 It's not happening down here, so this will help our method from this package here. 1:07 Now I'll strip strong tags. 1:11 So, strong was just the first problem that we're having as we are building this do 1:13 your own HTML sort of thing. 1:17 The next thing that started happening is people started putting their own links, 1:19 and people ended up actually leaving the site. 1:22 So, what our design team asked is if we could add a relic external 1:24 to any link that happens to be in there. 1:29 So let me just show you what that looks like. 1:30 So, we'll get the result. 1:32 We're gonna take a thing called externalize links and 1:34 I wanna parse in the results to that, right. 1:37 So this, Strips the bold, and 1:40 this we'll, Add rel = external. 1:44 So, now you could see when I go and run this, the link here has this rel external. 1:52 So one thing that we came up with as a team was we wanted to have a utility 1:58 function that we could just kind of use all over the place, right? 2:02 Because these fields are showing up all over the place. 2:06 So in our utilities package, we have a thing called Renderer. 2:09 And it has a method called render and it takes input. 2:13 So we're going to take this htmlInput and you can do things with it. 2:16 So we made it take a function, right? 2:21 Cuz that makes sense, cuz we wanna take a function that filters those things. 2:23 So, what we did originally was we just wanted to do, 2:25 both clearly like that, right. 2:28 And we'll go ahead, let's store this in the result here. 2:30 So that takes care of this this first one here but 2:36 it doesn't take care of this externalized links, right, because there's a bunch. 2:38 So what we ended up having to do in this is kind of gross, is we did this. 2:43 We took the text that was passed in and we have a little land of body here. 2:47 So now, we have these two things going on. 2:51 So we'll grab the html and will take the text in, and 2:54 then from here, we will grab whatever came out of there and 2:59 externalize the links,right? 3:03 And say, let's just do this. 3:10 So return, html right? 3:12 Plus the comments when I went back into that so here we go. 3:20 Still in the same thing basically right so it's taken this function and 3:23 it runs a function on it. 3:26 Now this is definitely a step in the right direction, right? 3:27 But I don't like the fact that people are going to just copy and 3:30 paste this bit here,right, because we need to do that every single time. 3:33 So, let's do this. 3:36 Let's look at these functions first. 3:38 So it's a string and it returns a string. 3:40 Each of the functions then here take a string and return a string. 3:44 Let's play with this a little bit. 3:48 Let's see. So 3:49 if I have a function and we make it a string. 3:50 String. 3:55 Let's call this boldCleaner. 3:57 And we can just use a method reference here. 4:01 So we can say Html:: boldCleaner; so 4:03 that's a function that we have our handle on there. 4:05 So I'm gonna lose this, let's do this. 4:08 So then, what she want to do is after we run this, we want to run externalize link. 4:12 So we want to run boldCleaner and then we want to run externalizeLinks. 4:18 Look at that? 4:26 That is called composing a method, okay. 4:28 So we've composed the two. 4:31 So the first method runs, the results from it is passed into the next one, 4:33 just like a chain. 4:36 So, as you can see I can actually highlight this. 4:38 When I go ahead and extract a variable and it called a filter. 4:42 Let's go ahead, let's call this sanitizer, okay. 4:49 So there is now a sanitizer, it does exactly what we wanted. 4:55 Now I can export this and I can take that wherever I want it, right. 4:58 So that's pretty clean looking there, isn't it? 5:01 And it's just doing those little function pipeline there. 5:03 And again, it runs boldCleaner and then it runs externalizeLinks, and 5:06 it pass a String all the way through. 5:11 So I don't know about you, but I'm ready for lunch and 5:13 I'm about ready to head out when I see a new feature request come through. 5:15 We now want to support Markdown. 5:19 Now, if Markdown is new to you, it's a text format and 5:20 it's used all over the place. 5:24 I see it on GitHub, you'll see it on a Wikis, different software bug trackers. 5:25 Now, it has a limited scope to HTML and it's a lot easier to edit. 5:30 Check the teachers notes for more. 5:34 But we wanna do here is, we wanna make sure that we can render Markdown. 5:36 Let's do that next video. 5:40
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