Rest Api Ruby On Rails Nested Models

Question

I'm kinda new to the whole rails/ruby thing. I've built a restful API for an invoicing app. Summary of models is below.

class Invoice < ActiveRecord::Base
    has_many :pages
end

class Page < ActiveRecord::Base
    belogs_to :invoice
    has_many :rows
end

class Row < ActiveRecord::Base
    belogs_to :page
end

I would like to be able to include related models in one rest call. I can currently do one level of nesting. For example i can get an Invoice with all its pages /invoices?with=pages is the call i would make. In controller i would create a hash array from this as per below(probably not the best code you've seen):

def with_params_hash
  if(params[:with])
    withs = params[:with].split(',')
        withs.map! do |with|
        with.parameterize.underscore.to_sym
    end
    withs
  else
    nil
  end
end

This will return a hash as array e.g [:pages]

In the controller i use it as

@response = @invoice.to_json(:include => with_params_hash)

This works fine. I would like to be able to include nested models of say page.

As you know this can be done this way:

@invoice.to_json(:include => [:page => {:rows}])

The first question i guess is how do i represent this in the URL? I was thinking: /invoices?with=pages>rows. Assuming thats how I decide to do it. How do i then convert with=pages>rows into [:pages => {:rows}]

After a quick scan of your problem (apologies if I miss vital info) The RESTful route for all rows would be: invoices/3/pages/5/rows - resource/id/resource/id/resource for lists and resource/id/resource/id for individual resources. Or just resource/id of course, depending on the problem. Also, see here: asciicasts.com/episodes/230-inherited-resources for something which may or may not help, but should give an idea of a Rails-ey way of handling nested resources. — A Fader Darkly
– A Fader Darkly, Commented Aug 28, 2014 at 12:41
@AFaderDarkly thanks for the reply. I've already got routes like invoices/3/pages, invoices/3/pages/5/rows and so forth. The reason i wanted to do this is so i can reduce overhead and minimise api calls. Cause if an invoice had 5 pages with 10 rows each. I'd have to make 5 More calls plus another 5 to get rows. I'd like to get everything at one go. Hope that helps. — Tali Luvhengo
– Tali Luvhengo, Commented Aug 28, 2014 at 13:32
Apologies, I see your problem. Why not default to serving a deep object (with relevant associations) as a sensible default use case, then allow a 'shallow' option to get just the parent object? Or do you require the ability to be specific about the included associations? — A Fader Darkly
– A Fader Darkly, Commented Aug 28, 2014 at 17:29

J. David Guerra · Accepted Answer · 2014-08-28 13:32:32Z

2

Why don't you use jbuilder? Will be easiest and you will can nest all models you want.

https://github.com/rails/jbuilder

answered Aug 28, 2014 at 13:32

J. David Guerra

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2 Comments

Tali Luvhengo Over a year ago

Hi @david was trying to avoid using views. But that's an excellent answer. I'd hate to have to rewrite/modify my controllers.

Tali Luvhengo Over a year ago

You know the fact that i'm lazy to change my code doesnt make this the wrong answer. So I changed to using Jbuilder. Worked okay. But in the end i prefered RABL github.com/nesquena/rabl

Tali Luvhengo · Accepted Answer · 2014-08-28 13:43:32Z

So i ended up going with the format below for url:

/invoices?with=pages>rows

The function below will generate the function required:

def with_params_hash
    final_arr = []
    with_array = params[:with].split(',')
    with_array.each do |withstring|
        if withstring.include? ">"
            parent = withstring[0..(withstring.index('>')-1)].parameterize.underscore.to_sym
            sub = withstring[(withstring.index('>')+1)..withstring.length].parameterize.underscore.to_sym
            final_arr << {parent => {:include => sub}}
        else
            final_arr << withstring.parameterize.underscore.to_sym
        end
    end
    final_arr
end

Usage in the controller looks like:

@invoice.all.to_json(:include => with_params)

Alternatively as per @DavidGuerra's idea https://github.com/rails/jbuilder is not a bad option.

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