我研究框架凤凰。 是将存储在云存储中的映像模型。在创建图像时,我计算文件的哈希值,并将其作为:名称。我做了一个模型,控制器和视图。但我不明白为什么会收到错误:
== Compilation error on file web/models/image.ex ==
** (CompileError) web/models/image.ex:26: undefined function changeset/3
(stdlib) lists.erl:1338: :lists.foreach/2
(stdlib) erl_eval.erl:670: :erl_eval.do_apply/6
(elixir) lib/kernel/parallel_compiler.ex:116: anonymous fn/4 in Kernel.ParallelCompiler.spawn_compilers/1
我已经查看了所有代码,但没有找到我用三个参数调用Image.changeset的地方。 我的image.ex:
defmodule Blog.Image do
use Blog.Web, :model
schema "images" do
field :name, :string
field :original_name, :string
field :filename, :string, virtual: true
timestamps
end
@required_fields ~w(
name
original_name
filename
)
@optional_fields ~w()
def changeset(struct, params \\ %{}) do
struct
|> cast(params, @required_fields, @optional_fields)
end
def create_changeset(struct, params \\ %{}) do
struct
|> changeset(struct, params)
|> generate_name_hash
end
defp generate_name_hash(changeset) do
put_change(changeset, :name, gen_hash_name(changeset[:filename]))
end
defp gen_hash_name(filename) do
hash_name = :crypto.hash(:sha256, File.read(filename))
|> Base.encode16
"/"<>slice(hash_name, 0, 2)<>"/"<>slice(hash_name, 2, 2)<>"/"<>slice(hash_name, 4, 2)
end
end
my image_controller.ex:
defmodule Blog.ImageController do
use Blog.Web, :controller
plug Addict.Plugs.Authenticated when action in [:new, :create]
def new(conn, _params) do
changeset = Blog.Image.changeset(%Blog.Image{})
render conn, "new.html", changeset: changeset
end
def create(conn, %{"image" => image_params}) do
full_image_params = %{filename: image_params["image"].path, original_name: image_params["image"].filename}
changeset = Blog.Image.create_changeset(%Blog.Image{}, full_image_params)
case Blog.Repo.insert(changeset) do
{:ok, image} ->
conn
|> put_flash(:info, "Image created successfully.")
|> redirect(to: image_path(conn, :show, image))
{:error, changeset} ->
render(conn, "new.html", changeset: changeset)
end
end
end
我的new.html.eex:
<%= form_for @changeset, image_path(@conn, :create), [role: "form", multipart: true], fn f -> %>
<div class="form-group">
<%= label f, :image, class: "control-label" %>
<%= file_input f, :image, class: "form-control" %>
<%= error_tag f, :image %>
</div>
<div class="container">
<div class="form-group">
<%= submit "Submit", class: "btn btn-default" %>
</div>
</div>
<% end %>
答案 0 :(得分:2)
我相信:
def create_changeset(struct, params \\ %{}) do
struct
|> changeset(struct, params)
|> generate_name_hash
end
应该是
def create_changeset(struct, params \\ %{}) do
struct
|> changeset(params)
|> generate_name_hash
end
因为|>
运算符传递了它左边的任何内容作为右边函数的第一个参数。所以你基本上在做changeset(struct, struct, params)
答案 1 :(得分:0)
堆栈跟踪可以准确地告诉您错误的位置:
** (CompileError) web/models/image.ex:26: undefined function changeset/3
。
我相信您正在尝试使用cast
函数,因为Ecto changesets本身不存在changeset
函数。此外,cast
有三个,所以你错过了一个参数。
在第26行更改此内容:
def create_changeset(struct, params \\ %{}) do
struct
|> changeset(struct, params)
|> generate_name_hash
end
到此:
def create_changeset(struct, params \\ %{}) do
struct
|> cast(params, [:name, :original_name, :filename]) #<---- 3rd arg. = 'allowed'
|> generate_name_hash
end
cast
函数需要三个参数cast(data, params, allowed)
。所有未明确允许的参数都将被忽略。
和Mchl说的一样,函数的结果传递给FIRST参数到管道操作中的下一个函数(在这个特定的帖子中你不需要明确地传递struct
)。