Render D3 graph from a string of JSON instead of a JSON file

Question

I am trying to render the following Dendrogram from my Rails app: http://bl.ocks.org/mbostock/4063570

I have a model with many attributes, but I would like to manual

Answer 1

First, lets look at what d3.json does.

d3.json("/assets/flare.json", function(root) {
    // code that uses the object 'root'
});

This loads the file /assets/flare.json from the server, interprets the contents as JSON and passes the resulting object as the root argument to the anonymous function.

Where you already have a JSON object, you don't need to use the d3.json function - you can just use the object directly.

var root = {
   "name": "flare",
   "children": [
     ...
   ]
};
// code that uses the object 'root'

If the object is represented as a string, then you can use JSON.parse to get the object:

var myString = '{"name": "flare","children": [ ... ] }';
var root = JSON.parse(mystring);
// code that uses the object 'root'

Second, lets look at what d3.layout.cluster expects of your data. As per the docs:

... the default children accessor assumes each input data is an object with a children array ...

In other words, you data needs to be of the form:

var mystring = '{
    "name": "Product",
    "children": [
        {
            "name": "id",
            "type": "number",
            "description": "Product identifier",
            "required": true
        },
        ...
        {
            "name": "stock",
            "type": "object",
            "children": [
                {
                    "name: "warehouse",
                    "type": "number"
                },
                {
                    "name": "retail",
                    "type": "number"
                }
            ]
        }
    ]
}

Answer 2

d3.json actually takes URL as an argument, so instead of giving it the path to the file, I would suggest to delegate data management to the controller (especially, if in future you would need to load it from DB), so to simplify things:

1. Create a method in your controller, which would actually open the file and return its content:

class YourFlareController < ApplicationController
    def load
        @data = File.read("app/assets/json/flare.json")
        render :json => @data
    end
end

1. Make sure you have a route in your routes.rb

get "yourflare/load"

1. And now in your javascript you can simply call

d3.json("http://host/yourflare/load", function(root) {