elixir - Phoenix.HTML.Form 不会从变更集中获取错误

Question

我有如下所示的模板代码:

<%= form_for @changeset, @action, fn f -> %>
  <%= if Enum.any?(f.errors) do %>
    <%= for {attr, message} <- f.errors do %>
      <li><%= humanize(attr) %> <%= message %></li>
    <% end %>
  <% end %>
<% end %>

但即使变更集包含错误，也不会打印错误。这是检查的表单结构。请注意，错误列表是空的，即使它是从带有错误的变更集构建的。

%Phoenix.HTML.Form{data: %BlogPhoenix.Comment{__meta__: #Ecto.Schema.Metadata<:built, "comments">,
  content: nil, id: nil, inserted_at: nil, name: nil, post_id: nil,
  posts: #Ecto.Association.NotLoaded<association :posts is not loaded>,
  updated_at: nil}, errors: [], hidden: [], id: "comment",
 impl: Phoenix.HTML.FormData.Ecto.Changeset, index: nil, name: "comment",
 options: [method: "post"],
 params: %{"content" => nil, "name" => nil, "post_id" => "1"},
 source: #Ecto.Changeset<action: nil, changes: %{},
  errors: [name: {"can't be blank", [validation: :required]},
   content: {"can't be blank", [validation: :required]}],
  data: #BlogPhoenix.Comment<>, valid?: false>}

这里发生了什么？不应该填充此错误列表吗？

Answer 1

您的变更集的 :action 为零，这就是隐藏错误的原因( see source )。

Ecto.Changeset docs (在“变更集操作”标题下)指出:

For example, frameworks such as Phoenix uses the value of changeset.action to decide if errors should be shown or not on a given form.

上面的文档建议了这种方法:

changeset = User.changeset(%User{}, %{age: 42, email: "mary@example.com"})

# Since we don't plan to call Repo.insert/2 or similar, we
# need to mimic part of its behaviour, which is to check if
# the changeset is valid and set its action accordingly if not.
if changeset.valid? do
  ... success case ...
else
  changeset = %{changeset | action: :insert} # action can be anything
  ... failure case ...
end