Complex Template Tags

You're doing great so far. 0:00 Now you're ready to write a template tag, that can serve as a navigation menu for 0:02 your site. 0:07 Basically, we want to add a menu on the left that lists all the courses, 0:08 and links to the course details page for each one. 0:13 It'll show up on each page, and make it easier to move around the site. 0:17 So let's get started. 0:22 Let's open up course extras.py again. 0:23 We need to create a new function, 0:27 so define nav courses list. 0:32 Again, this function isn't going to take any arguments. 0:37 We just want to get all of the courses and return them, so 0:41 this function is pretty straight forward. 0:44 Let's add a doc string that explains that. 0:47 So, Returns dictionary of courses to display as navigation pane. 0:49 We've already imported the course model, because we used it in our last template 0:59 tag, so now we just need to write our query. 1:03 So courses = Course.objects.all, and 1:06 then return dictionary, like we said we would, courses. 1:11 So we're assigning the variable courses 1:18 to the result of the query course.objects.all. 1:21 Which does exactly what it says. 1:25 It gets all of the course objects. 1:28 We then return those courses in a dictionary. 1:30 Before we're finished with course extras.py, we need to register this tag. 1:33 The type of tag we're writing here, is called an inclusion tag. 1:38 And it's different than a simple tag, 1:42 because it returns its data as a whole other template, not just a string. 1:45 That explains its name, 1:50 you're including another template in the template, in which you use this tag. 1:52 Registering our inclusion tag is therefore a little bit different, 1:58 than registering the simple tag we did before. 2:02 So we would type register.inclusion_tag, and then we pass in 2:06 the path to the template file that we haven't actually created yet. 2:11 But this is the template that we're going to include in another template whenever we 2:18 use this tag. 2:22 And then we also have to pass the name of the function. 2:23 We're using the same register variable, 2:30 which you remember is where we are keeping the call to the template.library class. 2:33 But instead of calling the simple tag method on that class, 2:38 we're calling the inclusion tag method. 2:41 We pass it the path to the template this tag gets included in, 2:44 as well as the name of the tag. 2:48 But that's a lot of typing. 2:50 And there's a shorter way to register inclusion tags. 2:52 Just like with our simple tag, we can use a decorator. 2:55 So let's delete that other registration function and 2:58 replace it with this decorator. 3:02 Register.inclusion_tag, and 3:03 then we just pass it that path, course_nav.html. 3:07 Now we need to code this template, this course_nav.html. 3:15 Remember since this is an inclusion tag, 3:19 we're creating a template that can be dropped in anywhere. 3:21 So over here in courses, create a new file called course_nav.html. 3:25 This next part should look familiar. 3:32 Since our function gets all of our courses for us, we can just open up a for loop and 3:35 do for course in courses, and open up a div, and use the course title. 3:40 Then we just need to close our for loop. 3:50 Now that's a great start, but since we're using this template to navigate among 3:54 the different courses in our site, we should probably add some links. 3:58 So right before course title, we'll open up an anchor tag. 4:03 And this is a great opportunity for us to review the URL tag and how it works. 4:06 So we pass in the primary key, 4:12 and we move the end of the anchor tag, to after our course title. 4:20 Now, let's review the URL tag. 4:26 We include the name of the URL, as the first argument to the URL tag. 4:28 That's the courses:detail part. 4:32 We included courses, because we've name spaced our URLs and 4:36 detail because that's the name we gave the URL we want to go in our urls.py file. 4:40 Go double check urls.py to see what I mean. 4:46 Then we've passed in the primary key PK that this specific URL needs. 4:50 We can't go to a details page, if we don't know which course we need details on. 4:56 Now, so that we always have this navigation section available to us, 5:01 let's drop it into our layout.html page. 5:05 We already have load course_extras up here, so 5:09 now right inside our site-container, 5:14 we can create a new div and just drop in nav_courses_list. 5:18 When we do our steps to start our server, which include changing directories into 5:26 our learning site, and then running python manage.py runserver on our port. 5:31 We can use the little i to see our navigation pane. 5:39 Now, in the real world, you would probably add some CSS to make this navigation pane 5:44 display across the top in a more attractive way, or 5:49 along the left hand side. 5:52 But we've proved our concept here, and so 5:54 I'll leave it to you to experiment with CSS in the ways that you want to. 5:56 Have fun. 6:00 I hope by this point you understand why custom template tags are useful and 6:02 how to get started with them. 6:07 Maybe you're already thinking of situations where writing your own template 6:09 tag, would make your own projects better and more flexible. 6:13 But did you know you can write your own filters too? 6:18 We'll do that in the next video, so stay tuned. 6:22