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POHow to show server errors in Rails 2.3.5 with JSON and jQuery
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  1. POHow to show server errors in Rails 2.3.5 with JSON and jQuery
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    copied!<p>I've got in-place editing on a page in my app (using Rails 2.3.5 and jQuery). I want to know how to display an error on the page when the update fails.</p> <p>I'm using ajax (an XMLHttpRequest) to save an update to a Comment object. The controller has an update method like this:</p> <pre><code>def update @comment = Comment.find(params[:id]) respond_to do |format| # if @comment.update_attributes!(params[:comment]) if false #deliberately forcing a fail here to see what happens format.json { render :nothing =&gt; true } else format.json { render :json =&gt; @comment.errors, :status =&gt; :unprocessable_entity } end end end </code></pre> <p>In Firebug, I can see the server returns a "422" (an appropriate validation error status code). But it's a response to an XMLHttpRequest so there is no redirect to an error page. </p> <p>I think I actually want to do this:</p> <pre><code>format.json { render :json =&gt; @comment.errors} </code></pre> <p>or maybe this:</p> <pre><code>format.json {render :json =&gt; { :status =&gt; :error, :message =&gt; "Could not be saved" }.to_json, :status =&gt; 400 } </code></pre> <p>and trigger some Javascript function that iterates through (and displays) any errors.</p> <p>I'm using a rails plugin <a href="http://github.com/janv/rest_in_place/" rel="nofollow noreferrer">REST in Place</a> to implement the in-place editing. It doesn't appear to have any callback function to handle a failure. What are my options? Can I write some Javascript to respond to a failure condition without hacking the plugin? Do I have to hack the rest_in_place plugin to handle a failure condition? Is there a better plugin (for Rails or jQuery) that handles in-place editing, including failure conditions?</p> <p><strong>UPDATE</strong></p> <p>This post from Peter Bui <a href="http://paydrotalks.com/posts/45-standard-json-response-for-rails-and-jquery" rel="nofollow noreferrer">Standard JSON Response for Rails and jQuery</a> was helpful in showing how to handle an error message from the server using <code>XMLHttpRequest.status</code>. I looked at his implementation of a blog using ajax <a href="http://github.com/paydro/talks" rel="nofollow noreferrer">paydro-talks</a>. I'm surprised at the complexity required to handle a simple error condition. Usually Rails has all the goodness baked in but it seems server errors with JSON are out of scope. Can that be?</p> <p>I also looked at grimen's <a href="http://github.com/grimen/validatious-on-rails/" rel="nofollow noreferrer">validatious-on-rails</a> which accommodates models validations when ajax XMLHttpRequest is used. It's not clear to me how I'd use it to handle the general case of a "save" failing when validations succeed.</p>
 

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