Ruby double pipe usage - ruby-on-rails

Question

I have a file which have different paths for remote server and local server.
Remote server path:
"/app/public/front-end/public/JSONModels/IdPairing/Text.json"
Local server path:
"public/front-end/public/JSONModels/IdPairing/Text.json"
I basically wanna make sure my app finds correct path for the file regardless of which server I'm at.
So I found something like double pipe ( || ) in Ruby syntax like below:
File.read("/app/public/front-end/public/JSONModels/IdPairing/Text.json" || "public/front-end/public/JSONModels/IdPairing/Text.json")
But it seems like it only reads the first path. How do you make sure it reads the second path if the file is not being found in the first path?
Thanks

Answer 1

A lazy way is:
begin
File.read("/app/public/front-end/public/JSONModels/IdPairing/Text.json")
rescue
File.read("public/front-end/public/JSONModels/IdPairing/Text.json")
end

Answer 2

Why it doesn't work for you:
irb(main):001:0> File.read("some made up name")
Errno::ENOENT: No such file or directory - some made up name
from (irb):1:in `read'
from (irb):1
from /usr/bin/irb:12:in `<main>'
irb(main):002:0> File.read("some made up name" || "Gemfile")
Errno::ENOENT: No such file or directory - some made up name
from (irb):2:in `read'
from (irb):2
from /usr/bin/irb:12:in `<main>'
As you can see, when you try to read a file that doesn't exist, Ruby explodes.
That's what exist? is for.
What you should do
irb(main):003:0> filename = File.exist?("some made up name") ? "some made up name" : "Gemfile"
=> "Gemfile"
irb(main):004:0> File.read(filename)
That's one way to do it, at least.

Answer 3

I would suggest to put those paths into an environment specific config file. Take a look at railsconfig/config on GitHub.
After you have installed the gem, you can add a configuration to config/settings/<RAILS_ENV>.yml like
json_file: /app/public/front-end/public/JSONModels/IdPairing/Text.json
where <RAILS_ENV> can be development, test, production or a custom environment.
And in your code, just
File.read(Settings.json_file)

Answer 4

If you want to try these in sequence, define a list first:
FILES = [
"/app/public/front-end/public/JSONModels/IdPairing/Text.json",
"public/front-end/public/JSONModels/IdPairing/Text.json"
]
Then you can simply open the first one that exists:
path = FILES.find { |f| File.exists?(f) }
File.open(path)
The problem was that "string" || "string" will never work, the first string is logically true and the rest is irrelevant and ignored.