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POUsing RJS to replace innerHTML with a real live instance variable
 

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  1. POUsing RJS to replace innerHTML with a real live instance variable
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    <p>I can't for the life of me get RJS to replace an element's innerHTML with an instance variable's attribute, i.e. something like <code>@thing.name</code></p> <p>I'll show all the code (simplified from the actual project, but still complete), and I hope the solution will be forehead-slap obvious to someone...</p> <p>In RoR, I've made a simple page displaying a random Chinese character.</p> <p>This is a <code>Word</code> object with attributes <code>chinese</code> and <code>english</code>.</p> <p>Clicking on a link titled "What is this?" reveals the <code>english</code> attribute using RJS. Currently, it also hides the "What is this?" link and reveals a "Try Another?" link that just reloads the page, effectively starting over with a new random character.</p> <p>This is fine, but there are other elements on the page that make their own database queries, so I would like to load a new random character by an AJAX call, leaving the rest of the page alone.</p> <p>This has turned out to be harder than I expected: I have no trouble replacing the html using link_remote_to and page.replace_html, but I can't get it to display anything that includes an instance variable.</p> <p>I have a Word resource and a Page resource, which has a home page, where all this fun takes place. In the PagesController, I've made a couple ways to get random words. Either one works fine...</p> <p>Here's the code:</p> <pre><code>class PagesController &lt; ApplicationController def home all_words = Word.find(:all) @random_word = all_words.rand @random_words = Word.find(:all, :limit =&gt; 100, :order =&gt; 'rand()') @random_first = @random_words[1] end end </code></pre> <p>As an aside, the SQL call with <code>:limit =&gt; 100</code> is just in case I think of some way to cycle through those random words. Right now it's not useful. Also, the 'rand()' is MySQL specific, as far as I know.</p> <p>In the home page view (it's HAML), I have this:</p> <pre><code>#character_box = render(:partial =&gt; "character", :object =&gt; @random_word) if @random_word #whatisthis = link_to_remote "☝ what is this?", :url =&gt; { :controller =&gt; 'words', :action =&gt; 'reveal_character' }, :html =&gt; { :title =&gt; "Click for the translation." } #tryanother.{:style =&gt; "display:none"} = link_to "try another?", root_path </code></pre> <p>Note that the #'s in this case represent divs (with the given ids), not comments, because this is HAML.</p> <p>The "character" partial looks like this (it's erb, for no real reason):</p> <pre><code>&lt;div id="character"&gt; &lt;%= "#{@random_word.chinese}" } %&gt; &lt;/div&gt; &lt;div id="revealed" style="display:none"&gt; &lt;ul&gt; &lt;li&gt;&lt;span id="english"&gt;&lt;%= "#{@random_word.english_name}" %&gt;&lt;/span&gt;&lt;/li&gt; &lt;/ul&gt; &lt;/div&gt; </code></pre> <p>The reveal_character.rjs file looks like this:</p> <pre><code>page[:revealed].visual_effect :slide_down, :duration =&gt; '.2' page[:english].visual_effect :highlight, :startcolor =&gt; "#ffff00", :endcolor =&gt; "#ffffff", :duration =&gt; '2.5' page.delay(0.8) do page[:whatisthis].visual_effect :fade, :duration =&gt; '.3' page[:tryanother].visual_effect :appear end </code></pre> <p>That all works perfectly fine.</p> <p>But if I try to turn <code>link_to "try another?"</code> into <code>link_to_remote</code>, and point it to an RJS template that replaces the "character" element with something new, it only works when I replace the innerHTML with static text. If I try to pass an instance variable in there, it never works.</p> <p>For instance, let's say I've defined a second random word under Pages#home...</p> <p>I'll add <code>@random_second = @random_words[2]</code> there.</p> <p>Then, in the home page view, I'll replace the "try another?" link (previously pointing to the <code>root_path</code>), with this:</p> <pre><code>= link_to_remote "try another?", :url =&gt; { :controller =&gt; 'words', :action =&gt; 'second_character' }, :html =&gt; { :title =&gt; "Click for a new character." } </code></pre> <p>I'll make that new RJS template, at app/views/words/second_character.rjs, and a simple test like this shows that it's working:</p> <pre><code>page.replace_html("character", "hi") </code></pre> <p>But if I change it to this:</p> <pre><code>page.replace_html("character", "#{@random_second.english}") </code></pre> <p>I get an error saying I fed it a nil object:</p> <blockquote> <p>ActionView::TemplateError (undefined method `english_name' for nil:NilClass) on line #1 of app/views/words/second_character.rjs: 1: page.replace_html("character", "#{@random_second.english}")</p> </blockquote> <p>Of course, actually instantiating @random_second, @random_third and so on ad infinitum would be ridiculous in a real app (I would eventually figure out some better way to keep grabbing a new random record without reloading the page), but the point is that I don't know how to get any instance variable to work here.</p> <p>This is not even approaching my ideal solution of rendering a partial that includes the object I specify, like this:</p> <pre><code>page.replace_html 'character', :partial =&gt; 'new_character', :object =&gt; @random_second </code></pre> <p>As I can't get an instance variable to work directly, I obviously cannot get it to work via a partial.</p> <p>I have tried various things like:</p> <pre><code>:object =&gt; @random_second </code></pre> <p>or</p> <pre><code>:locals =&gt; { :random_second =&gt; @random_second } </code></pre> <p>I've tried adding these all over the place -- in the <code>link_to_remote</code> options most obviously -- and studying what gets passed in the parameters, but to no avail. It's at this point that I realize I don't know what I'm doing.</p> <p>This is my first question here. I erred on the side of providing all necessary code, rather than being brief. Any help would be greatly appreciated.</p>
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