Qqwy
Using Plug.Upload in your changesets
Hello Everyone,
I am working on a small Phoenix/Ecto project. One of the features of this application is going to be that people can upload images. Right now I am using arc (and arc_ecto) to make the uploading procedure easier.
However, I want to store the dimensions and other metadata of the image that has been saved in the database as well, to make it nicer to display it in a gallery later.
I know there are multiple packages on Hex.pm that allow you to do this, such as fastimage, but these libraries work with a pathname to the file.
- Exactly how can I make a library that takes a pathname consume a
%Plug.Upload{}struct? I believe it contains a:pathfield, but I have been unable to build a%Plug.Upload{}manually to try it out. There is documentation of Plug.Upload, but it is rather short and uninformative (does the:pathfield include or exclude the actual filename itself, or only its folder? How do you make a%Plug.Upload{}struct manually?). - Related to this: How can you test file-uploading code? I am interested in doing both a feature-test, testing only if when you have a file if the dimensions are read and added to the changeset properly, and a full-stack test where a file is selected from the browser and it is then attempted to be uploaded.
Any help is greatly appreciated!
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josevalim
When you do it as post(conn, table_upload_path(conn, :create, table_upload: params)), you are passing the parameters as part of the query string, i.e. as part of the URL. You need to pass it as part of the post:
conn = post(conn, table_upload_path(conn, :create), table_upload: params)
arkgil
IIRC, when I was working with file uploads in tests, I was creating Plug.Upload struct manually and passed it as regular parameter to get, post etc. macros in controller tests:
post conn, image_path(conn, :create), upload: %Plug.Upload{...}
EDIT: but of course the question is about changesets
I think @OvermindDL1 is with the right approach.
Qqwy
All right! I have since learned that the :path field is a path to a temporary file (including the filename itself). The :filename is the name used during uploading, which can be used to do (a weak form of!) MIME-checking, and possibly to store it in your app, etc.
I was able to call ImageMagick using the extracted :path. (Yes, this code should be cleaned up and get some documentation, but it’s a proof-of-concept.)
defmodule Cmd.Magick do
def dimensions(file_path) do
case System.cmd("identify", ["-format","%w %h", Path.expand(file_path)]) do
{res, 0} ->
[width, height] =
res
|> String.split
|> Enum.map(&String.to_integer/1)
%{width: width, height: height}
{_other, _} ->
raise ArgumentError
end
end
end
In my Phoenix 1.3 changeset function I’ve added a call to this function to the pipeline:
def add_image_dimensions(changeset, attrs) do
case attrs["image"] do
%Plug.Upload{path: path, filename: filename} ->
changeset
|> cast(Cmd.Magick.dimensions(path), [:width, :height])
path when is_binary(path) ->
changeset
|> cast(Cmd.Magick.dimensions(path), [:width, :height])
_ ->
changeset
end
end
This works!
What I am yet to figure out though, is how this code can be tested properly. Please help!







