Building Data-Driven Web Apps with Flask and SQLAlchemy Transcripts
Chapter: Routing and URLs
Lecture: Adding a constrained route
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Now let's go and add
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the rest of the routes to our application here.
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So we've got our home_views
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with index and about.
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I got packages.
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Let's go and create another one of these.
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So we have our blueprint
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for project details.
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But what I want to do is just get the popular ones.
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Now I want to do something really cool with this
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so let's just have this return.
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Details for most popular package.
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It's not going to be exactly perfect
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but now I'm going to pass in a rank
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and it's going to be an integer like so.
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How do we do that in the URL?
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So what I want to do actually is
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I'd like to be able to come over here.
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Is this going to work?
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let me just make a quick change here.
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Now it should run.
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What I want to do is something pretty awesome.
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So if we go over here and we say /about
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we get this. If I say /project/something
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I get something else. But I want to say
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if the thing happens to be a number like 7
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or 5 or 4 or whatever
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I want to run just this function.
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Now if it was
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abc I still want it to do 'not found'.
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But if it's just the number right
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like show me the fifth most popular one
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I would like to pull up that package details.
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I'll give you an example of that as well.
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So if we go over to talkpaython.fm
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website podcast and you go to the episode
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you can see they have great long URL names
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like /episodes/show/206
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and then a shortened sort of friendly version
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of the title. But sometimes it's nice
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sometimes you just want to share really quickly
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oh like hey that was show 206 like this.
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If you click that and check that out
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it goes right over.
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Want to know what show 205 was?
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There you go, that's what it is.
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So there's this cool way
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to capture only integers.
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There's other stuff that shows up there.
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Like if I go to just /episodes
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that matches but I want to say if it's an integer
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we're going to pull it from the database.
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So let's see that over here.
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And there's a pretty slick way to do this.
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I'm going to go and just say
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we're going to have a /<int:rank>
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and this is going to be a variable.
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So we want to say this
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but only in the case that it's an integer.
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So there's a way to do that in Flask.
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You just say int:rank.
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And now if we go and run this
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and we go I want to go to about
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we get about. But if I want to go to /7
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details for the seventh most popular package.
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/5, fifth most popular package.
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But we can still go to all the rest of our site
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is still working just fine.
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Isn't that cool?
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So anytime you want to have
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some sort of constraint like this
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we can put the type in front and also
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let's just do a real quick print
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type of rank and the value of rank
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real quick there. And let's look again at 11.
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See that Flask already converts that
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to an integer.
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So it's not like working in string
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but it could be an int.
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No it's actually converted to an integer for us
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which is pretty cool. And if it goes abc
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it doesn't match that route
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so it just says 404.
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If we didn't have that integer constraint
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you know potentially that would hit
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and cause a problem right.
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So if we don't have that here for example
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now I can see details for the abc-th.
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That doesn't even make any sense right.
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So we can say only match this short
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sort of Flask / some value
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if it happens to be an integer.
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Really cool we're going to add
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the popular route that way.
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Now the details are not implemented yet
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we'll get to that.
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But a pretty cool way to add
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this specific route here.
