6: Modeling and Viewing Users, Part I in Java

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6: Modeling and Viewing Users, Part I
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Finally, we ll add the show action to the Users controller (corresponding to the
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showhtmlerb view) with the code in Listing 625, which defines the @user instance
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variable needed by the view
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Listing 625 The Users controller with a show action
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app/controllers/users_controllerrb
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class UsersController < ApplicationController def show @user = Userfind(params[:id]) end def new @title = "Sign up" end end
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Here we ve gotten a little ahead of ourselves by using the standard Rails params object to retrieve the user id When we make the appropriate request to the Users controller, params[:id] will be the user id 1, so the effect is the same as the find command
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Userfind(1)
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we saw in Section 614 Although the show view and action are now both defined, we still don t have a way to view the page itself This requires defining the proper rule in the Rails routes file, as we ll see in the next section
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633 A Users Resource
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Our method for displaying the user show page will follow the conventions of the REST architecture favored in Rails applications This style is based on the ideas of representational state transfer identified and named by computer scientist Roy Fielding in his doctoral dissertation Architectural Styles and the Design of Network Based Software Architectures24
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24 Fielding, Roy Thomas Architectural Styles and the Design of Network Based Software Architectures Doctoral dissertation, University of California, Irvine, 2000
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Viewing Users
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The initial effect of hitting /users/1
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The REST design style emphasizes representing data as resources that can be created, shown, updated, or destroyed four actions corresponding to the four fundamental operations POST, GET, PUT, and DELETE defined by the HTTP standard (Box 31) When following REST principles, resources are typically referenced using the resource name and a unique identifier What this means in the context of users which we re now thinking of as a Users resource is that we should view the user with id 1 by issuing a GET request to the URL /users/1 Here the show action is implicit in the type of request when Rails REST features are activated, GET requests are automatically handled by the show action Unfortunately, the URL /users/1 doesn t work quite yet due to a routing error (Figure 69) We can get the REST-style Users URL to work by adding users as a resource to config/routesrb, as seen in Listing 626
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6: Modeling and Viewing Users, Part I
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Listing 626 Adding a Users resource to the routes file
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config/routesrb
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SampleApp::Applicationroutesdraw do resources :users match '/signup', end :to => 'users#new'
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After adding the routes for the Users resource, the URL /users/1 works perfectly (Figure 610)
The user show page at /users/1 after adding a Users resource
Viewing Users
Table 62 RESTful routes provided by the Users resource in Listing 626 HTTP Request URL
/users /users/1 /users/new /users /users/1 /edit PUT /users/1 DELETE /users/1 GET GET GET POST GET
Action
index show new create edit
Named Route
users_path user_path(1) new_user_path users_path edit_user_path(1)
Purpose page to list all users page to show user with id 1 page to make a new user (signup) create a new user page to edit user with id 1 update user with id 1 delete user with id 1
update user_path(1) destroy user_path(1)
You might have noticed that Listing 626 removed the line
get "users/new"
last seen in Listing 529 This is because the one additional resource line in Listing 626 doesn t just add a working /users/1 URL; it endows our sample application with all the actions needed for a RESTful Users resource,25 along with a large number of named routes (Section 523) for generating user URLs The resulting correspondence of URLs, actions, and named routes is shown in Table 62 (Compare to Table 22) Over the course of the next three chapters, we ll cover all of the other entries in Table 62 as we fill in all the actions necessary to make Users a fully RESTful resource
params in debug Before leaving the user show page, we ll take a moment to examine the debug information produced by Listing 623 If you look closely at Figure 610, you ll see that it includes useful information about the page being rendered:26
25 This means that the routing works, but the corresponding pages don t necessarily work at this point For example, /users/1/edit gets routed properly to the edit action of the Users controller, but since the edit action doesn t exist yet actually hitting that URL will return an error 26 Some of this tutorial s screenshots show debug information with output like !map:HashWithIndifferentAccess instead of !map:ActiveSupport::HashWithIndifferentAccess This is simply a minor difference between Rails 23 and Rails 3 Since the rendered web pages are otherwise identical between Rails versions, this one footnote saves me the trouble of redoing all the screenshots