nesimtunc
Can't access application environment variables as boolean
Hi,
I set some application environment variables based on System’s environment variables in config.exs file like this:
And access it from DevicePlug module like this:
While I get access these values properly from another modules without problem, for example:
but I get error in DevicePlug module and it returns “false” as string instead of a boolean variable. Why?
Here’s a full stack error log:
[info] GET /
[debug] Processing with ColivingWeb.PageController.index/2
Parameters: %{}
Pipelines: [:browser]
"false"
[info] Sent 500 in 59ms
[error] #PID<0.468.0> running ColivingWeb.Endpoint (connection #PID<0.467.0>, stream id 1) terminated
Server: localhost:4000 (http)
Request: GET /
** (exit) an exception was raised:
** (CaseClauseError) no case clause matching: "false"
(coliving 0.1.0) lib/coliving_web/plugs/device_plug.ex:20: ColivingWeb.Plugs.DevicePlug.call/2
(coliving 0.1.0) ColivingWeb.Router.browser/2
(coliving 0.1.0) lib/coliving_web/router.ex:1: ColivingWeb.Router.__pipe_through0__/1
(phoenix 1.5.1) lib/phoenix/router.ex:347: Phoenix.Router.__call__/2
(coliving 0.1.0) lib/coliving_web/endpoint.ex:1: ColivingWeb.Endpoint.plug_builder_call/2
(coliving 0.1.0) lib/plug/debugger.ex:132: ColivingWeb.Endpoint."call (overridable 3)"/2
(coliving 0.1.0) lib/coliving_web/endpoint.ex:1: ColivingWeb.Endpoint.call/2
(phoenix 1.5.1) lib/phoenix/endpoint/cowboy2_handler.ex:64: Phoenix.Endpoint.Cowboy2Handler.init/4
(cowboy 2.7.0) coliving/deps/cowboy/src/cowboy_handler.erl:41: :cowboy_handler.execute/2
(cowboy 2.7.0) coliving/deps/cowboy/src/cowboy_stream_h.erl:320: :cowboy_stream_h.execute/3
(cowboy 2.7.0) coliving/deps/cowboy/src/cowboy_stream_h.erl:302: :cowboy_stream_h.request_process/3
(stdlib 3.11.2) proc_lib.erl:249: :proc_lib.init_p_do_apply/3
Thanks!
Marked As Solved
NobbZ
In your config.exs (or a similar file) you are doing this:
config :foo, :bar, System.get_env("ENV")
As System.get_env/1 always returns a string (the system environment isn’t even able to store something else), Application.get_env(:foo, :bar) will of course return a string as well.
If you want to read a “boolean” from the enf, you need a little helper:
toBool = fn
"true", _ -> true
"false", _ -> false
nil, default -> default
end
config :foo, :bar, toBool.(System.get_env("ENV"), false)
This will crash when the config is evaluated and ENV is not set correctly.
Also Liked
Nicd
Environment variables are always strings. If you wish to cast them to a different type, you need to do that manually.
Be careful about getting environment variables in your config.exs files, as they are evaluated during build time and will reflect the build environment. When you move to production, you probably want to be able to get the values at startup / runtime instead. I just wrote a blog post about the different places of configuration.
NobbZ
App env can be whatever you want, system environment though is string only.
Nicd
Not sure what you mean by this. The main thing to think about is that the normal config files are evaluated at build time, but config/releases.exs is evaluated at startup time.
I should probably clarify that in the article. The init functions are just a convention that many libraries use, but Phoenix does not use it. So that’s why it’s never called. The example uses Geolix which does allow setting an init function to be called at startup.
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