Access heroku environment variable in coffeescript file

Question

I have a scenario where I want my CoffeeScript file to access an environment variable like an API key value. This works fine locally but it isn't working when I push it up to heroku.

The file is named something like myfile.js.coffee.erb

I am setting the value like this

api_key = '<%= ENV['SERVICE_API_KEY'] %>'

I know the values are set in heroku and I have triple checked the spelling, etc. I know it is being processed since the resulting JavaScript file looks like this

var api_key;
api_key = "";

Is there something I need to do when precompiling my assets where I can tell it to access environment variables? I admit that I am new to CoffeeScript and the Rails asset pipeline. Is there another more accepted way of doing this? I don't want to embed it in the file for obvious reasons.

I am making the project open source so I don't want my api keys in the source. — Adam Carr
– Adam Carr, Commented Jul 28, 2012 at 5:10
Ah, gotcha; I misunderstood what you meant by embedding it in the file. — Colin R
– Colin R, Commented Jul 28, 2012 at 5:12
Also, locally I want to use different api keys so by using ENV vars, it allows me to not have to change the file for each environment manually. — Adam Carr
– Adam Carr, Commented Jul 28, 2012 at 5:12
Yeah, I definitely agree with not hardcoding them; I just quickly read that and thought you were worried about others seeing the key. — Colin R
– Colin R, Commented Jul 28, 2012 at 5:20

Colin R · Accepted Answer · 2012-07-28 05:15:12Z

4

So since the API key is going to be visible to those interested whether it's in the javascript file or the html file and since you really don't want to be generating a new .js file every request, the easiest solution I've found to the same problem is to put the key in your layout.html.erb file.

You can throw it in a script tag, use a data-attr, whatever floats your boat, but it works and you get the benefit of a dynamic variable and having to render one less file.

And you can still use the <%= ENV['api_key'] %>. You'll have to fetch the variable in your js (or coffee), but that's pretty trivial.

answered Jul 28, 2012 at 5:15

Colin R

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3 Comments

Adam Carr Over a year ago

Yeah, I have thought about that like setting window.API_KEY in the layout or setting a body data attribute and accessing it that way and will probably end up going that route if needed. I just figured there should be a way to accomplish this on Heroku since I can do it locally but maybe not.

Colin R Over a year ago

You could always try compiling the assets on heroku (heroku run bundle exec rake assets:precompile) - which I haven't tried, but I've had this same issue and I solved it by taking advantage of data-attributes in my views.

Adam Carr Over a year ago

Tried that already and that didn't work. I'll probably go with the data-attr route but am still interested if there is a way to solve this on heroku.

Community · Accepted Answer · 2017-05-23 12:31:52Z

2

Try this

heroku labs:enable user_env_compile -a myapp

then deploy again

Worked for us!

all credits to this guy: Heroku always runs assets:precompile with the production environment for Rails 3.2

edited May 23, 2017 at 12:31

CommunityBot

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answered Aug 24, 2012 at 11:21

G.T.

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