ColonelKurtzEx (CKEX)

ColonelKurtzEx facilitates working with the block content editor Colonel Kurtz in Phoenix applications. The main faculties ColonelKurtzEx provides are focused on structured data, validation, and rendering.

Documentation is available on GitHub and will be on HexDocs soon!

Note on terminology: For clarity and conciseness, this document may refer to the elixir library as CKEX and the javascript library as CKJS.

Table of Contents

  1. Overview
  2. Installation
  3. Getting Set Up
  4. FAQs
  5. Development
  6. Contributing
  7. Authors
  8. License


Colonel Kurtz (CKJS)

Colonel Kurtz is a block content editor implemented in JS.

It is recommended that you have a reasonable understanding of CKJS and how to use it before diving into CKEX. Specifically, how the data is structured and how to extend its functionality with new block types. Head over to the repo for more information.

Here's a brief summary of the basics to better orient you to some concepts relevant to CKEX:

  1. CKJS produces a (potentially deeply) nested tree of blocks in JSON format.
  2. A block has the following fields: type, content, and blocks (the latter represents any nested child blocks).
  3. When you define a CKJS block type, you implement it using a React Component which affords you great flexibility when it comes to the UI you present to users of your application.
Structured Data

Anyone familiar with Elixir and the surrounding community is likely to already understand the benefits of structured data. This isn't an essay on the subject but suffice to say that we believe in using named structs and predictable data wherever possible. One of the main motivations of ColonelKurtzEx is to convert CKJS JSON into named structs.


Data integrity is crucial to building robust software and validation is important for helping users create valid data through providing helpful error messages. ColonelKurtzEx gives developers the ability to validate CKJS JSON data by leveraging Ecto Changesets which should be familiar to many Elixir developers. If you've done anything with databases or validation you've likely used Ecto and will be familiar with how to implement validation rules for CK data using CKEX.


ColonelKurtzEx provides a BlockTypeView macro that can be used in Phoenix Views. A block type view, aside from being a normal Phoenix View (used to handle presentation of data), controls whether a block can render by specifying an implementation for renderable?/1. The default is true, but modules that use the macro may override this method to enable more fine-grained control over whether a block should be rendered based on its current data.

For example, you might need to model a block that requires exactly 3 images to be defined in its data. If a greater or lesser number is specified, the block type view can disable rendering (e.g. to prevent invalid layouts from happening). However, you should try to implement these rules in your block type validation to prevent invalid data from reaching the database in the first place.


If available in Hex, the package can be installed by adding colonel_kurtz_ex to your list of dependencies in mix.exs:

def deps do
    {:colonel_kurtz_ex, "~> 0.1.0"}

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at


The root module for ColonelKurtzEx (ColonelKurtz) defines the most commonly used API methods when interacting with the library. It delegates all of the implementation to various other submodules. In most cases you won't have to think too hard about where to import things from unless you're reaching for a function that's less commonly used.

Getting Set Up

To get set up with ColonelKurtzEx, you'll need to install and configure Colonel Kurtz. Since the two libraries go hand in hand, you'll often jump back and forth between the two. For example, when you add a new block type to CKJS, you'll need to add the corresponding modules for CKEX (a BlockType, BlockTypeView, and template). In the future CKEX will provide generators to expedite the process of common tasks such as adding a new block type.

Note: The following sections are expandable (and are collapsed by default).

1. Add Folders for BlockTypes and BlockTypeViews

After adding the library to your dependencies, you'll want to define a few modules in the scope of your application. One for your custom BlockType definitions, and one for your BlockTypeViews.

Note: it is important that each of these concepts live inside a dedicated module namespace in your application so that the library can look up specific block type and view modules at runtime.

See an example

For example, assuming a standard phoenix project structure:

  1. Create a new subfolder inside lib/your_app_web/views/, using whatever name you'd like that corresponds with the module you'll be defining views inside (e.g. lib/your_app_web/views/blocks/ folder and YourAppWeb.Blocks module.).

  2. Create a new subfolder inside lib/your_app/. Again, the name doesn't matter so long as you configure ColonelKurtzEx correctly (more information in the following section). For example, you might create a folder named lib/your_app/block_types/ and to contain the YourApp.BlockTypes namespace.

2. Configure ColonelKurtzEx

Add the following to your config/config.exs to allow CKEX to locate your custom BlockType and BlockTypeView modules:

config :colonel_kurtz_ex, ColonelKurtz,
  block_views: YourAppWeb.Blocks,
  block_types: YourApp.BlockTypes

3. Add a CK field to one of your app's schemas
  1. First, amend the schema to add a new field that will hold your CKJS data:

    defmodule YourApp.Post do
      use Ecto.Schema
      # 1. alias the custom ecto type
      alias ColonelKurtzEx.CKBlocks
      # 2. import the validation helper
      import ColonelKurtzEx.Validation, only: [validate_blocks: 2]
      schema "posts" do
        field :title, :string
        # 3. add a field of this type, named whatever you like
        field :content, CKBlocks, default: []
      def changeset(post, params \\ %{}) do
        # 4. make sure you cast the new field in your changeset
        |> cast(params, [:title, :content])
        # 5. call `validate_blocks` passing the name of your field
        |> validate_blocks(:content)

    Note: validate_blocks/2 can take an atom or a list of atoms if you have more than one set of blocks fields to validate.

  2. Then create the migration to add the field to your database

    mix ecto.gen.migration add_content_to_posts
  3. CKBlocks expects the underlying field to be a :map which is implemented as a jsonb column in Postgres.

    # priv/repo/migrations/<timestamp>_add_content_to_posts.exs
    defmodule YourApp.Repo.Migrations.AddContentToPost do
      use Ecto.Migration
      def change do
        alter table("posts") do
          add :content, :map
  4. Run your migration

    mix ecto.migrate

4. Teach your Phoenix Views how to render blocks
  1. Use ColonelKurtz.render_blocks/1 to render block content somewhere in a template.

    More information

    You may import this method as needed in the views that will render blocks. Or, as a convenience, you may import this function automatically in all of your phoenix views by adding it to the your_app_web.ex definition for view (or view_helpers if you want it to be available for live views as well, example below).

  2. In addition, to render the block editor in your forms, you'll want to pull in ColonelKurtz.render_blocks/1 too. The example below shows how to do this for all Phoenix Views in your application.

    See an example
    # lib/your_app_web.ex
      # ...
      defp view_helpers do
        quote do
          use Phoenix.HTML
          import Phoenix.LiveView.Helpers
          import BlogDemoWeb.LiveHelpers
          # 1. import `render_blocks/1` so that it is available for all views
          import ColonelKurtz, only: [render_blocks: 1, block_editor: 2]
          # 2. optional: import all of the form helpers if you want to use other functions
          #    (such as `blocks_json/2` or `block_errors_json/2`)
          import ColonelKurtz.FormHelpers
          import Phoenix.View
          import BlogDemoWeb.ErrorHelpers
          import BlogDemoWeb.Gettext
          alias BlogDemoWeb.Router.Helpers, as: Routes
      # ...
  3. Render your blocks inside your view's show template:

    # lib/your_app_web/templates/post/show.html.eex
    # ...
    <%= render_blocks @post.content %>
    # ...
  4. Render the block editor field inside your view's form:

    # lib/your_app_web/templates/post/form.html.eex
    # ...
    <%= label f, :content %>
    <%= error_tag f, :content %>
    <%= block_editor f, :content %>
    # ...

    Note: The block_editor helper outputs some markup that you must mountCKJS on.

5. Add your custom BlockTypes

Note: As of this writing, there remains a lot of work to do in order to provide a default set of useful block types, some of which are already provided by CKJS, along with generators to aide in the creation of new block types.

  1. Create your BlockType module: Continuing from the example scenario outlined above, create a new block type at lib/your_app/block_types/image.ex where image is just an example of a descriptive name of the block you're modeling.

    # lib/your_app/block_types/image.ex
    # 1. optional, you may choose to define the `<type>Block` module if you need to add validation
    #     at the block level (for most use cases you can skip this step; it's only necessary if
    #     you need to validate e.g. that a block has a particular number of child `:blocks`).
    defmodule YourApp.BlockTypes.ImageBlock do
      use ColonelKurtz.BlockType
      def validate(_block, changeset) do
        # e.g. this block must have at least 1 child block
        |> validate_length(:blocks, min: 1)
    # 2. define the `<type>Block.Content` module within your configured `:block_types` namespace
    defmodule YourApp.BlockTypes.ImageBlock.Content do
      # 3. use the BlockType macro
      use ColonelKurtz.BlockTypeContent
      # 4. use the `embedded_schema` macro to specify the schema for your block's content
      embedded_schema do
        field :src, :string
        field :width, :integer
        field :height, :integer
      # 5. optional, but encouraged - define your validation rules for the block's content
      def validate(_content, changeset) do
        |> validate_required([:src, :width, :height])
        # ... any other custom validation rules you need ...
  2. Create your BlockView: create a new block view at lib/your_app_web/blocks/image_view.ex.

    Note: make sure you've configured ColonelKurtzEx with the location of your block_views and block_types. See "Configure ColonelKurtzEx" above.

    # lib/your_app_web/blocks/image_view.ex
    defmodule YourAppWeb.Blocks.ImageView do
      use YourAppWeb, :view
      use ColonelKurtz.BlockTypeView
      # optionally implement `renderable?/1`
      def renderable?(%ImageBlock{content: %{src: ""}} = block), do: false
      def renderable?(_block), do: true


How can I inspect the block data or errors in a nice format?

Take a look at the functions provided in ColonelKurtz.FormHelpers, specifically blocks_json/3 and block_errors_json/3. Both of these methods accept a third argument which is a list of options to pass to Jason.Encoder (hint: try pretty: true).

How does ColonelKurtzEx look up my custom block type and view modules?

You configure the :block_views and :block_types options for CKEX in your config.exs by providing the modules in your app that will contain your custom block types and views. When CKEX marshalls blocks JSON, it parses data into lists of maps using Jason and then looks up a block type based on the block's type field.

It does so by calling Module.concat with the module you specified for :block_types and Macro.camelize(type) <> "Block" (e.g. "image" => YourApp.BlockTypes.ImageBlock).

Similarly, to lookup your view modules CKEX calls Module.concat with the module you specified for :block_views and Macro.camelize(type) <> "View" (e.g. "image" => YourAppWeb.Blocks.ImageView).

My block type schema changed, how can I migrate my existing block data?

Congratulations, you've discovered an unsolved Hard Problemâ„¢.

We're currently working on a proposal for library changes that might better facilitate data migrations on CK block JSON.

In the meantime, it is recommended to leverage your RDBMS's capabilities for querying and modifying JSON. Our best advice for now is: As much as you can, try to avoid the need to migrate CK JSON data.


Code Quality

To help maintain high code quality this project uses dialyxir and credo for static code analysis, ExUnit for testing and ExCoveralls for test coverage.


mix dialyzer

Code Style

mix credo --strict


mix test


  1. Fork the library
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request


  • Solomon Hawk (@solomonhawk)
  • Dylan Lederle-Ensign (@dlederle)


ColonelKurtzEx is released under the MIT License. See the LICENSE file for further details.