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101 lines
2.5 KiB
Markdown
101 lines
2.5 KiB
Markdown
# Union Forms
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When building a form for a union, you use `inputs_for` as normal, but a few things are done for you under the hood.
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Lets take this example union:
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```elixir
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defmodule NormalContent do
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use Ash.Resource, data_layer: :embedded
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attributes do
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attribute :body, :string, allow_nil?: false
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end
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actions do
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defaults [:read, create: [:body], update: [:body]]
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end
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end
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defmodule SpecialContent do
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use Ash.Resource, data_layer: :embedded
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attributes do
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attribute :text, :string, allow_nil?: false
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end
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actions do
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defaults [:read, create: [:text], update: [:text]]
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end
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end
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defmodule Content do
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use Ash.Type.NewType,
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subtype_of: :union,
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constraints: [
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types: [
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normal: [
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type: NormalContent,
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tag: :type,
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tag_value: :normal
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],
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special: [
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type: SpecialContent,
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tag: :type,
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tag_value: :special
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]
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]
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]
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end
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```
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## Determining the type for a union form
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We track the type of the value in a hidden param called `_union_type`. You can use this to show a different form depending on the type of thing.
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## Changing the type of a union form
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If you want to let the user _change_ the union type, you would use `AshPhoenix.Form.remove_form/3` and `AshPhoenix.Form.add_form/3`. See the example below for the template, and here is an example event handler
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```elixir
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def handle_event("type-changed", %{"_target" => path} = params, socket) do
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new_type = get_in(params, path)
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# The last part of the path in this case is the field name
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path = :lists.droplast(path)
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form =
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socket.assigns.form
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|> AshPhoenix.Form.remove_form(path)
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|> AshPhoenix.Form.add_form(path, params: %{"_union_type" => new_type})
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{:noreply, assign(socket, :form, form)}
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end
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```
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## Non-embedded types
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If one of your union values is a _non_ embedded type, like `:integer`, it will still be a nested form, but you would access the single value with `<.input field={nested_form[:value]} .../>`
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## Example
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We might have a form like this:
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```heex
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<.inputs_for :let={fc} field={@form[:content]}>
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<!-- Dropdown for setting the union type -->
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<.input
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field={fc[:_union_type}
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phx-change="type-changed"
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type="select"
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options={[Normal: "normal", Special: "special"]}
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/>
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<!-- switch on the union type to display a form -->
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<%= case fc.params["_union_type"] do %>
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<% "normal" -> %>
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<.input type="text" field={fc[:body]} />
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<% "special" -> %>
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<.input type="text" field={fc[:text]} />
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<% end %>
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</.inputs_for>
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```
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