Question

I have Rails application that needs to retrieve data from a SOAP server outside of my control. It retrieves a list of users with statistics attached to them and returns the data as JSON.

Once that data is retrieved, I need to combine it with data retrieved from my Rails app database.

Once I have the JSON from the SOAP server in hand, I send it up to a Rails controller so that new values can be added to the JSON and then sent back to the view.

My problem is a very simple one. I can’t seem to read and iterate through the JSON once it’s in my controller.

JS from my view stat_data is the JSON received from the SOAP service

window.get_metrics = (stat_data) ->
    update_loading_message 'Getting Metrics'
     console.log stat_data

    $.ajax '/tracking/get_metrics',
        type: "POST"
        data: client_data: stat_data
        dataType: 'json'
        success : (data) ->
            console.log(data)
            # populate_table(data)

Controller

@client_advisors = params[:client_data]
puts @client_advisors

# This is where I would do my other processing / model calls to get new data

render file: 'tracking/metrics_data.json.erb', content_type: 'application/json'

Output of puts @client_advisors

{
"0"=>
{
"personnel_id"=>"1495", 
"personnel_name"=>"John Smith",
"statistic_x"=>"200"
}, 
"1"=>
{
"personnel_id"=>"5266",
"personnel_name"=>"John Candy",
"statistic_x"=>"300"
},
"2"=>{
... etc ...
}
}

tracking/metrics_data.json.erb

[
<%= puts '~~~~~~~~~~~~  PROCESSING JSON' %>
<% @client_advisors.each do |advisor| %>

<%= puts 'advisor::' %>
<%= puts advisor %>
<%= puts 'advisor.inspect::' %>
<%= puts advisor.inspect %>
{   
... This is where my re-generated JSON would go

}
<% end %> 
]

I ridiculously can’t seem to target a personnel_name or personnel_id in my metrics_data.json.erb. It’s outputting each full advisor object just fine in the console… But I’m not sure what I should be using to target the object’s values. I’ve tried advisor.personnel_name (obviously won’t work because the objects are named "0, 1, 2, etc"), advisor['0'], advisor[0], advisor[:0]. None allow me to go a level deeper and retrieve the personnel_name.

Your time is most appreciated!

Solved!

Thanks to @willglynn

"jQuery – somewhat surprisingly – has no mechanism to create JSON. It can parse just fine, but you have to encode it yourself. You can use JSON.stringify , but for ahem certain browsers, you need JSON2.js" – @willglynn

Updated JS

window.get_metrics = (stat_data) ->
    update_loading_message 'Getting Metrics'
     console.log stat_data

    $.ajax '/tracking/get_metrics',
        type: "POST"
        data: client_data: JSON.stringify(stat_data)
        dataType: 'json'
        success : (data) ->
            console.log(data)
            # populate_table(data)

Updated controller

@client_advisors = JSON.parse(params[:client_data])

Updated tracking/metrics.erb.json

<% puts advisor %>
<% puts advisor['personnel_id'] %>

Answer 1

To answer your question, when Rails gets a POST of JSON content, it transforms the request content into something looking like a form submission. This means that params[] won’t exactly match the original object. To get the original object back, you need to go behind Rails’ back and parse it out of the request directly:

@client_advisors = ActiveSupport::JSON.decode(request.body.read)

That said, there are a number of things I would change about this code.

• You have a SOAP server that returns JSON, and this is somehow getting sent to your Rails app. What component does that? Why? Could you cut out the middleman and make Rails talk directly to the SOAP component?
• You’re generating JSON with string concatenation in an erb template. This is error-prone and tedious. Instead, use render :json => [{ 'key' => 'value' }].
• You’re putting lots of knowledge into the view. This is a normal place to start, but it’s not ideal. I would probably make a model that encapsulates the response from this SOAP component — not ActiveRecord, just a Ruby object — and make that model responsible for interacting with my other models to have the desired effects.

That last one is important, since it would let you eliminate your view and reduce the controller to something like:

@soap_thing = CrazySoapThing.parse(request.body.read)
@soap_thing.sync
render :json => @soap_thing.affected_records

See Skinny Controller, Fat Model for more.