RoR+CouchBase构建社交应用

jieforest

You may get a conflict error at this point saying the model already exists. Don’t worry, just say ‘N’ to not overwrite it.  You may also see an error Couchbase not found.  Again, don’t worry about this, as I stated above Couchbase-Model isn’t compatible with the Rails Model generator.

If all went to plan, you should now have a vines_controller.rband a whole views folder for vines with the frontend HAML or ERB files.  Go ahead and open up vines_controller.rb and make sure it reflects the file here.

In our controller file, you may have noticed a method called‘upvote’.  This is the voting mechanism for our Vine videos.  The finish the implementation of this voting system, and to actually give the Vine videos a place to live, open up the fileapp/views/vines/show.haml(or .erb)

Make sure it relfects the file found here...

Before our voting system will work completely, we need to add the following to our routes.rb file:

1. 1.resources :vines do
   
2. 2.member do
   
3. 3.put :upvote
   
4. 4.end
   
5. 5.end
   

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jieforest

Ok, so now our Vine videos can be displayed, and the voting mechanism is in place!  The next thing we need to do is setup the main page for the app – The Leaderboard!  Our leaderboard, although being the main feature of the app, is incredibly simple.  Open up the file app/views/vines/index.haml (or .erb)  and ensure it matches the code here.

Now, if this were any ordinary relational Rails app, we should in theory have a leaderboard already created, listing each Vine video in our database.  BUT this isn’t the case here.
In Couchbase, we need to create our leaderboard using Views in Couchbase and utilising the Map/Reduce technique before we get a leaderboard that actually works properly!  

So, let’s do that!  Before we proceed here, if you haven’t used Couchbase Views prior to this, I recommend you read these docs, to give you a good bit of background knowledge on what Couchbase Views are, how we use them and to ease your way into using them in this Rails application

For our application, we need to create a View in Couchbase, that outputs each vine, with it’s Score and Title.  They also need to be ordered, descending, by Score so the Vine video with the highest score is naturally at the top of the Leaderboard.

jieforest

IF you have used Couchbase Views before, you may have created them from within the Admin console itself.  Views can be created from within the Admin UI, from any of our SDK clients and by means of the REST API.  

In this case, Couchbase-Model has a unique, and rather brilliant way of allowing us to generate Views for our application. Have a quick read of these docs to see how it can be done, and how we’re about to do it.

In Terminal, simply run:

1. rails generate couchbase:view vine all

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jieforest

Now, in your  app/models directory, you should have a new sub-directory named vine, with a subdirectory named all.  This directory contains 2 .js files – our map.js and reduce.js.  For now, all we’re interested in the map.js file.  Go ahead and open it up, and enter the following:

1. 1.function(doc, meta) {
   
2. 2.if (doc.type == "vine" && doc.title) {
   
3. 3.emit(doc.score, doc.title);
   
4. 4.}
   
5. 5.}
   

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As we can see from this Map function; we are wrapping the entire thing in an IF statement.  This is a best practice within Couchbase to check for attributes before trying to emit rows into our Index.  In this case, our IF statement is ensuring only docs with the type == “vine” and ensuring the vine has a title.  The emit function is then creating a row in our index using the document Score as the indexed key.  We are also outputting the document Title as the output value.

The reason we are outputting the Score as the Indexed key, is that we can take advantage of the Unicode Sorting that Couchbase automatically applies to this field.  In our case, we need to ensure our Score’s are descending, to push the highest scoring Vine to the top of the Leaderboard.  This map function will work fine on it’s own, and if you ran the application now, you will have a list of Vine videos, but they would be in the wrong order!

jieforest

It’s time to apply another feature of Couchbase to polish off our Leaderboard and ensure it works as it should.  It’s time to Query our View to create our final product.  Once again, Couchbase-Model allows us to do this straight from our Rails code.  Open up your model file  vine.rb  and add the following line just above the ‘private’ declaration:

1. view :all, :limit => 10, :descending =>true

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Not only is this code necessary to add query params to our View, but it must be added to our Vine.rb file with or without query parameters to ensure our application knows which View(s) it has to use in our application.  In this case, we can see, not only are we defining which view our application is to use, but we have also added the query parameters:

1. :limit => 10, :descending => true

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jieforest

By doing so, we are limiting the View’s output to 10 results and we are ensuring the Score is in descending order.Without much care to styling, we should have something that looks like this:

jieforest

over.