How to iterate through a nested array in a JSON object (Rails)

Question

How can I iterate over an array nested as a value inside a JSON object? This will be rendered in a .html.erb file.

This results in displaying the actual array in the view.

<% @data.each do |y| %>
    <%= y["name"] %>
    <%= y["location"] %>

    <%= y["cars"] %>

    <%= y["married"] %>
<% end %>

This results in an undefined method 'each' for nil:NilClass.

<% @data.each do |y| %>
    <%= y["name"] %>
    <%= y["location"] %>

    <% y["cars"].each do |z| %>
        <%= z["make"] %>
        <%= z["value"] %>
    <% end %>

    <%= y["married"] %>
<% end %>

JSON

[
    {
        "name":"Jim",
        "location":"London",
        "cars": [
                    {
                        "make":"Audi",
                        "value":"100k"
                    }
            ],
        "married": "Y"
    },
    {
        "name":"Sarah",
        "location":"New York",
        "cars": [
                    {
                        "make":"Ferrari",
                        "value":"200k"
                    },
                    {
                        "make":"Lambo",
                        "value":"350k"
                    } 
            ],
        "married": "Y"
    },
]

Has anyone successfully implemented this with JSON in a Rails template before?

Малъ Скрылевъ · Accepted Answer · 2016-05-31 21:20:00Z

1

Have you parsed JSON before in controller/service with JSON.parse? I asked because that is strange case when you have empty y["cars"] in array... in some cases...

If yes stub nil value for :cars in if it is empty with an empty array []:

<%- (y["cars"] || []).each do |z| %>
    <%= z["make"] %>
    <%= z["value"] %>
<%- end %>

and do better it with a decorator (see draper gem).

answered May 31, 2016 at 21:20

Малъ Скрылевъ

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