Questions & Ideas

[czak]

Don't know if there's a Google Group or anything, so I'm just posting here. I've been working on a REST API for a Rails app for the past 2 months and just discovered rabl. It might be something I've been looking for. Converted a few resources from as_json to .json.rabl and it seems cool so far.

I've got a few questions/ideas.

---

1. What's the proper way to extend a @object template from a @collection template?

I've got a posts resource and want to re-use the show template in the index template vibratim. Here's what I've come up with:

posts/show.json.rabl:

object @post
attributes :id, :body

posts/index.json.rabl:

collection @posts
extends 'posts/show'

It seems clumsy, but it works. I was kind of expecting a partial somewhere here. What would be the proper way to do that?

---

2. Using regular ifs within a template

Instead of the :if => lambda { ... } pattern, I tried using regular ifs within a template:

posts/show.json.rabl

object @post
attributes :id, :body

if @post.published?
  code(:publisher) { |p| p.publisher.username }
end

This works also, but presents a problem when using extends as presented above. The controller for an index action only provides the @posts collection, so the @post is nil and the if always fails when rendering the index action. I think it would be cleaner to use regular ifs. Especially when adding multiple custom fields - this would just be a single if block instead of multiple code(:field, :if => lambda { ... repeating condition ... }) blocks.

Maybe the way to do it could be - instead of relying on instance variables, provide an object or collection helper, which can always access the current object? Kind of like RSpec utilises subject.

---

3. Conditional child elements

I needed to include an entire subresource based on a condition. This didn't work:

child(:user, :if => lambda { ... }) do
  ...
end

So I eventually went with:

code(:user, :if => lambda { ... }) do |p|
  {
    :id => p.user.id,
    :username => p.user.username
  }
end

This works, but breaks DRY. I have a users/show.json.rabl with properly defined attributes, and would like to re-use it here. How would I go about it?

---

All in all, thanks for the great work. These are just some of my thoughts, Markdown-formatted. I'd be glad to dig into the code if you see any point in my mumbling ;) Cheers!

[nesquena]

Hey thanks for your feedback, much appreciated. Here is some thoughts and answers.

1. I am the first to admit my API isn't perfect but the way you demonstrated is how I do it too. I use extends in the object to inherit the properties. I don't view that inheritance case as a place for partials. I tend to use partials exclusively in code blocks when I want access to the json hash for another object. I tend to use extends in most other cases as you showed there. I don't view it as too clumsy but if you have a better approach I am happy to consider it for the future.
2. I like this idea but for implementation reasons (when dealing with a collection of objects) with the way RABL is currently set up having access to the object in a collection directly isn't easily possible. It can only be accessed in a lambda and passed it at the time each object is rendered. I can imagine a refactoring of RABL that could support an current_object helper that achieves the effect but I probably won't be doing that personally anytime soon unless it becomes an essential use case for me. Thanks for the suggestion and I welcome a patch :)
3. I completely agree that child should accept an if lambda. In fact I am pretty sure it does or did. I use child with if blocks in a couple of my APIs. Are you absolutely certain that they don't work? Notice the call to resolve_conditions here: https://github.com/nesquena/rabl/blob/master/lib/rabl/builder.rb#L77. If this doesn't work it is a bug and I will fix that soon hopefully.

Thanks again for your feedback and for trying RABL.

[wtn]

This post was very helpful. It was not immediately clear how to reuse templates from the README.

[xecutioner]

child (:auto_judge, :if => lambda {|station| station._type == "HumanWorker"}) {....}

gives out <pre><code>(eval):7: syntax error, unexpected ',', expecting ')' child (:auto_judge, :if =&gt; lambda {|station| sta... ^

[nesquena]

Is that a space after child? Might be the issue

child(:auto_judge, :if => lambda {|station| station._type == "HumanWorker"}) {....}

should work fine...what ruby are you using?

[xecutioner]

i'm using 1.9.2 child(:line,:if => lambda {@line!=nil}){... } still no effect??? i'm really stuck on this, am i doing something wrong???

[nesquena]

@xecutioner If it really doesn't work, hopefully I can fix it in the next release, I will have to play around. In the meantime try to use:

child @line => :line do
  # ...
end unless @line.nil?

[nesquena]

Closing this but adding a link the wiki, the bugs mentioned here should be fixed.

[tymate-team]

Seems bug is back child (@products, :if => lambda {|product| product.active?}) do

eval):4: syntax error, unexpected ',', expecting ')' child (@products, :if => lambda {|product| product.active?}) do

[nesquena]

It might be the space before the paranthesis, can you try:

child @products, :if => lambda {|product| product.active?} do
# ...
end