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Rails Routes and Resources

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Linking to Pages

3:56 with Jay McGavren

Users can view a list of all our page titles, but they can't view the content of single Pages yet. For our Posts resource, they can click a link on the list of all Posts to view an individual post. Let's set up links to view single Pages as well.

The link_to method returns a string with the HTML for a link.

<%= link_to("link text", "/link/path") %>

More documentation is here.

Let's say we need to set up links to view individual Page objects. In the URL path, following /pages/, we need a string representing the ID of the Page object we want to load. We'll set up the route like this:

get '/pages/:id', to: 'pages#show'

The colon followed by a name is a URL parameter. A URL parameter captures part of the request path, and makes it available within the controller in the params hash. So if we type :id here, it will be available later as params[:id]. We can name the parameter whatever we want, but by convention the name :id is used for model record IDs.

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    [MUSIC] 0:00
    Users can view a list of all our page titles but 0:05
    they can't view the content of single pages yet. 0:07
    For a post resource they can click a link on the list of all posts to view 0:10
    an individual post. 0:13
    Let's set up links to view single pages as well. 0:15
    We wanna turn these page titles into links, so we can click on them and 0:19
    view the associated page. 0:23
    Remember how we showed you that all saved rails model objects have an ID 0:25
    attribute that's used to look them up in the database. 0:28
    Creating links is one major reason that ID attribute exists. 0:32
    We're going to use that ID in our links to tell rails which model objects to load. 0:36
    We can embed dynamic HTML links into the output with output embedding tags. 0:40
    Within rails views, a helper method named link_to is available. 0:49
    It returns the necessary HTML string for creating a link. 0:53
    link_to's first argument should be the link text that you wanna displayed. 0:57
    And the second argument should be the path that you want the browser to request. 1:01
    If we save this we'll have web links in our output, let's say link text and 1:09
    that point to the nonexistent path of slash link, slash path. 1:14
    We can see the HTML output in our browser's developer tools. 1:19
    There's the link text within the anchor tag and 1:24
    there's the path of the link references. 1:26
    Now let's update this call to link_to and make it do something useful. 1:30
    We'll change the link text argument to be the page object's title. 1:34
    And we'll change the link path to the double quoted string slash pages slash 1:39
    page ID. 1:44
    And there's that idea attribute. 1:47
    We interpreted into the path string, so 1:49
    that the post with an idea of one creates a link to slash pages slash one. 1:51
    A post with an idea of three creates a link to slash pages slash three and so on. 1:55
    If we save this and reload our browser we'll see our updated links. 2:01
    But we can't actually click on them yet. If we try it we'll see an error, no route 2:05
    matches [GET] /pages/4, or whatever the idea of the link we tried to click on is. 2:09
    We need to go into the configs/route.rb file to fix this. 2:16
    We've set up a route for slash pages by itself but 2:22
    there's no route for slash pages followed by an ID. 2:25
    Let's set one up. 2:29
    Since the browser is requesting to load a page. 2:30
    It's going to be an HTTP get request. 2:32
    So, we'll set up another get route. 2:35
    We want it to match requests for paths that start with slash pages slash, so 2:37
    we'll add that string next. 2:42
    But following slash pages slash we're expecting a string representing the ID 2:45
    of the page object we want to load, so will type colon ID. 2:49
    The colon followed by a name is a URL parameter. 2:54
    A URL parameter captures part of the request path and 2:58
    makes it available within the controller in the params object. 3:01
    You may remember that we used params before to access form submission contents. 3:04
    So, if we type colon ID here, 3:09
    it will be available later in the params object under the ID key. 3:11
    We can name the parameter whatever we want. 3:15
    But by convention, the name ID is used for model record IDs. 3:17
    On the route for the list of all pages we specify which control or and 3:22
    which action should handle the requests. 3:25
    We need to do the same for the route for individual pages. We'll add a second 3:27
    argument to get with a key of two and a value of pages pound sign show that 3:33
    will direct requests of the show action on the pages controller. 3:38
    Let's save our work and now if we click on the /pages/4 link at our browser, 3:43
    we'll be routed to the show action on PagesController, 3:49
    of course we haven't created that method yet but will take care of that in a bit. 3:52

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