First App View

Let's make a view in our app that will list our all of the available courses. 0:00 We'll have to do a query to select all of the courses, 0:04 but I'm sure you remember how to do that from the last video. 0:06 If you want, feel free to pause me right now and try to build the view and 0:09 URL yourself. 0:12 We've already done all of these steps, so you should be able to get most, 0:12 if not all of it, without me. 0:17 So as you probably guessed, we're going to start in courses, views.py. 0:19 Here we are in our views.py. 0:23 Django provided us with an import here at the top, 0:26 a function named render that you haven't seen before. 0:28 This is actually really, really handy for when we want to start using templates. 0:32 For this first view though, let's just return plain text like we did before. 0:35 Which means that we need to import 0:41 the HttpResponse class again. 0:45 And of course we have to create a new view. 0:51 Now I think since this view is going to show a list of courses, 0:53 I'm gonna name it course list. 0:57 And you can, of course, name it anything that you want. 1:00 And as always, it takes a request. 1:03 Now since we want to use our course model, we should import it. 1:06 So I'm gonna add that up here from .models, 1:09 which the dot means look for the models module in the current directory. 1:13 Import Course. 1:17 Take out that comment. 1:20 Okay, so course list, what do we want to do in course list? 1:22 Now I can use the model to select everything. 1:26 And then I'm gonna use that. 1:29 And I'll merge that together into a string that joins all the titles, and 1:31 I'll send that back. 1:35 Okay so we'll just have all the titles. 1:36 So let's say courses equals course.objects.all. 1:38 And then we'll say the output equals comma space dot join courses, 1:44 and then we'll return HttpResponse of output. 1:50 Okay, so we select all of the courses that exist. 1:55 We join them together with commas, and 2:01 then we return an HttpResponse that has all those names joined by commas. 2:04 Now, of course, to see this view we have to create a URL for it. 2:09 This is a little bit interesting when you want to do it for an application and 2:13 you wanna do it cleanly. 2:17 So let's take this slowly. 2:18 So first things first, of course. 2:20 We don't have a urls.py in our app, so we should create one. 2:23 So we'll say new file, urls.py. 2:26 Cool, there it is. 2:32 Okay, easy enough. 2:33 Now what goes in here? 2:35 Well, the only thing that we need to import is the URL object from Django. 2:36 And we also have to import our views. 2:42 So, lets take care of the Django import first. 2:45 From django.comf.urls import url. 2:48 And then from .import views. 2:52 Nothing special there. 2:56 We've done these two lines before. 2:57 We had both of these imports, in fact, in our site-wide urls that we made. 3:00 Back up a stage or so. 3:05 Now, if you remembered those or cheated and looked at them, then you know 3:06 that we have to create our URL patterns variable, and fill it up with our URLs. 3:11 It's kind of weird that you have to name the variable exactly URL patterns. 3:16 Python isn't usually so proscriptive, but of course, this is Django, 3:20 not just standard Python. 3:23 Django can make whatever rules that it wants, and this is a rule that it made. 3:25 Let's make our variables. 3:29 So urlpatterns equals, and it's just a list. 3:31 If you've done old Django, it didn't use be just a list. 3:34 It's so nice now that it's just a list. 3:38 So we're gonna do url. 3:40 And it's gonna start and stop, and then we're gonna save views.course_list. 3:44 I gave this the same url as our home page, is that going to matter? 3:51 Well, let's see. 3:55 Let's run the server again, manage.py runsever. 3:56 0.0.0:8000 and let's open up our preview. 4:01 Oh, I accidentally did 8080. 4:10 There we go, 8000. 4:12 So we've got Hello World! 4:14 So no it didn't matter, we still get the home page. 4:16 Now that's partly because our courses.url.py isn't 4:19 even being loaded by Django at the moment. 4:23 Django doesn't automatically look for urls.py inside of apps, and 4:25 we haven't told it to look there, so it hasn't. 4:28 Okay, let's change that. 4:32 Come back over here and let's go to our urls.py for the project. 4:34 Alright, this is our big one, right? 4:40 And we're gonna add a new line, and we're gonna put it in before this admin line. 4:42 We're gonna get to what that admin is here in a little bit, but 4:48 right now let's just add in this new line. 4:51 So we're gonna say that it starts with courses, and 4:53 we're going to include courses.urls, and then a comma. 4:58 Now, the include function here, this one right here, 5:05 lets us include a set of URL patterns from somewhere else. 5:10 In this case, we're including them from our Courses app. 5:14 But why is it in quotes? 5:18 Django turns that string that we give it, so, this is just a string. 5:19 Turns that string into an import path, which let's it find the URL patterns. 5:24 And this means that we don't have to import the URLs ourselves into every 5:29 place that we want to use them. 5:32 This really, really helps with the plugableness and 5:35 modularity that I keep bringing up. 5:37 Okay, so now, let's find out, did the home page change? 5:40 No. 5:45 What if we go to slash courses? 5:46 And we've got a problem. 5:51 We got an error. 5:52 At least that's something though right? 5:53 Since we included the course URLs at slash courses and 5:54 the only URL we have there is just an empty string, so 5:58 long as nothing comes after courses, we get that course list view. 6:00 Unfortunately though, that view has a bug. 6:04 Let's see if we can fix that. 6:06 So our problem is that we got a course at the beginning, and 6:09 it expected a string instance. 6:13 Let's go back over here and look at our view. 6:14 Now we're using join and join expects everything in here to be strings. 6:17 Well those aren't all strings, those are courses. 6:22 So we're gonna fix that with a quick little list comprehension. 6:25 So we're gonna say we're gonna join str of courses ,or of course rather, for. 6:29 For course in courses. 6:43 Then let's close our list there, okay, STR course for course in course. 6:45 If this line is a little gibberishy for you, I'd suggest checking out 6:55 the comprehensions workshop that we have here on treehouse. 6:59 I'll link to it in the teacher's notes. 7:02 Basically, what we have is a for loop inside of a list, so 7:04 that it creates a list by working through the for loop. 7:07 It's a really handy construct. 7:10 Okay, so does this fix the bug? 7:11 It did! 7:15 Check that out. 7:16 There is the list of our courses, so excellent. 7:17 Congratulations on your first Django view that uses the ORM. 7:21 That's a giant achievement! 7:24 But, as I bet you can imagine, no one wants to have to go into the Django shell 7:26 to create all of their model instances. 7:29 There has to be a better way and there is. 7:31 The Django admin, that URL we've had from the beginning, is coming up next. 7:33