Modifying JSON - easy or difficult?

You probably have many technical challenges to face in your work. Some of them are time-consuming, others fast to solve. Sometimes you face problems very well understandable and potentially easy to solve … but in the end, you see that plenty of hours were consumed to find a solution that should take less than an hour.

So… how about modifying JSON? Is it easy or difficult in Ruby (& Rails)?

Let's assume we have a simple structure with HTML fragments within:

{
  "a": {
    "b": [
      {
        "c": "<span id=\"head\"></span>"
      },
      {
        "d": "<span id=\"body\"></span>"
      }
    ],
    "e": "#ffffff"
  },
  "f": "<span id=\"footer\"></span>",
  "g": 123
}

and we have a list of variables like:

head = "Hey John!"
body = "I invite you to my Birthday party!"
footer = "Best regards."

Our goal is to find specific DOM fragments within that tree and inject text. Other values cannot be changed. So we'll end with something like that.

{
  "a": {
    "b": [
      {
        "c": "<span id=\"head\">Hey John!</span>"
      },
      {
        "d": "<span id=\"body\">I invite you to my Birthday party!</span>"
      }
    ],
    "e": "#ffffff"
  },
  "f": "<span id=\"footer\">Best regards.</span>",
  "g": 123
}

Looks like the solution is quite simple. You can convert it to hash and use the deep_transform_values method in combination with the nokogiri gem.

hash.deep_transform_values { |value|
  if value.is_a?(String)
    html = Nokogiri::HTML5.fragment(value)

    head_node = html.at_css("#head")
    body_node = html.at_css("#body")
    footer_node = html.at_css("#footer")

    head_node&.inner_html = head
    body_node&.inner_html = body
    footer_node&.inner_html = footer

    html.to_s
  else
    value
  end
}

… and that's all.