How to mark a checkbox 'checked' with liveview?

Phoenix Forum Questions / Help
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1

Background

I am using Phoenix’s templating language with ~H and I want to mark some checkboxes as checked depending on some condition.

To achieve this, I have this code:

 defp syndicate_checkbox(assigns) do
    assigns = Enum.into(assigns, %{})

    if Map.get(assigns, :checked) do
      ~H"""
      <div class="row single-syndicate">
        <input class="column single-checkbox" type="checkbox" id={@synd.id}
                name="syndicates[]" value={@synd.id} checked>

        <label for={@synd.id} class="column"><%= @synd.name %></label>
      </div>
    """
    else
      ~H"""
      <div class="row single-syndicate">
        <input class="column single-checkbox" type="checkbox" id={@synd.id}
                name="syndicates[]" value={@synd.id}>

        <label for={@synd.id} class="column"><%= @synd.name %></label>
      </div>
    """
    end
  end

Now, this function works but all the duplication leaves a terrible taste in my mouth.

Specifically because the only difference here is this 1 line:

 <input class="column single-checkbox" type="checkbox" id={@synd.id}
                name="syndicates[]" value={@synd.id} checked>

Namelly, the checked word.

Problem

Normally I would do something like:

 <input class="column single-checkbox" type="checkbox" id={@synd.id}
                name="syndicates[]" value={@synd.id} {mark_checked(true)}>

and somewhere in the same file:

defp mark_checked(true), do: "checked"
defp mark_checked(_), do: ""

However the issue with this is that "checked" or "" are strings, which means the code inside ~H will not compile.

Question

How do I remove this duplication?

1 Like
2

<input … checked={boolean_value}> just works.

More generally I’d suggest using changesets for forms and let the helpers deal with the details.

1 Like