Responding to Ajax requests in the Relationships controller in Java

Encoding DataMatrix in Java Responding to Ajax requests in the Relationships controller
Listing 1236 Responding to Ajax requests in the Relationships controller
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app/controllers/relationships_controllerrb
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class RelationshipsController < ApplicationController before_filter :authenticate def create @user = Userfind(params[:relationship][:followed_id]) current_userfollow!(@user) respond_to do |format|
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15 At this point you will have to include the default Prototype JavaScript Library into your Rails application as in Listing 1039 if you have not done so already
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A Web Interface for Following and Followers
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formathtml { redirect_to @user } formatjs end end def destroy @user = Relationshipfind(params[:id])followed current_userunfollow!(@user) respond_to do |format| formathtml { redirect_to @user } formatjs end end end
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This code uses respond_to to take the appropriate action depending on the kind of request16 The syntax is potentially confusing, and it s important to understand that in
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respond_to do |format| formathtml { redirect_to @user } formatjs end
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only one of the lines gets executed (based on the nature of the request) In the case of an Ajax request, Rails automatically calls a JavaScript Embedded Ruby (jserb) file with the same name as the action, ie, createjserb or destroyjserb As you might guess, the files allow us to mix JavaScript and Embedded Ruby to perform actions on the current page It is these files that we need to create and edit in order to update the user profile page upon being followed or unfollowed Inside a JS-ERb file, Rails automatically provides the Prototype JavaScript helpers to manipulate the page using the Document Object Model (DOM) Prototype provides a large number of methods for manipulating the DOM, but here we will need only two First, we will need to know about the Prototype dollar-sign syntax to access a DOM element based in its unique CSS id For example, to manipulate the follow_form element, we will use the syntax
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$("follow_form")
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16 There is no relationship between this respond_to and the respond_to used in the RSpec examples
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12: Following Users
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(Recall from Listing 1223 that this is a div that wraps the form, not the form itself) The second method we ll need is update, which updates the HTML inside the relevant element with the contents of its argument For example, to replace the entire follow form with the string "foobar", we would write
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$("follow_form")update("foobar")
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Unlike plain JavaScript files, JS-ERb files also allow the use of Embedded Ruby, which we apply in the createjserb file to update the follow form with the unfollow partial (which is what should show after a successful following) and update the follower count The result is shown in Listing 1237
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Listing 1237 The JavaScript Embedded Ruby to create a following relationship
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app/views/relationships/createjserb
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$("follow_form")update("<%= escape_javascript(render('users/unfollow')) %>") $("followers")update('<%= "#{@userfollowerscount} followers" %>')
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The destroyjserb file is analogous (Listing 1238) Note that, as in Listing 1237, we must use the escape_javascript to escape out the result when inserting HTML
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Listing 1238 The Ruby JavaScript (RJS) to destroy a following relationship
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app/views/relationships/destroyjserb
$("follow_form")update("<%= escape_javascript(render('users/follow')) %>") $("followers")update('<%= "#{@userfollowerscount} followers" %>')
With that, you should navigate to a user profile page and verify that you can follow and unfollow without a page refresh Using Ajax in Rails is a large and fast-moving subject, so we ve only been able to scratch the surface here, but (as with the rest of the material in this tutorial) our treatment gives you a good foundation for more advanced resources It s especially worth noting that, in addition to Prototype, the JavaScript framework jQuery has gotten a lot of traction in the Rails community Implementing the Ajax functions from this section using jQuery is left as an exercise; see Section 125
The Status Feed
123 The Status Feed
We come now to the pinnacle of our sample application: the status feed Appropriately, this section contains some of the most advanced material in the entire tutorial Making the status feed involves assembling an array of the microposts from the users being followed by the current user, along with the current user s own microposts To accomplish this feat, we will need some fairly advanced Rails, Ruby, and even SQL programming techniques Because of the heavy lifting ahead, it s especially important to have a sense of where we re going A mockup of the final user status feed, which builds on the proto-feed from Section 1133, appears in Figure 1218