Added Poison as dependency

[sjoulbak]

Hi @JakeStaTeresa I’m back with my fix :)

Until today we were using my fix branch of Currencies and I wanted to update Currencies to the newest version. Unfortunately the UndefinedFunctionError exception was still there.

So I started to investigate why this exception was thrown. In #12 ensure_compiled/1 was added to ensure that @currencies isn’t set when the dependency Poison isn’t compiled first.

To come back to the ensure_compiled/1 function, this function return an tuple with {:module, module} or {:error, :embedded | :badfile | :nofile | :on_load_failure}. I’ve tested what this if-statement does with these tuples,

iex> if {:module, Test}, do: true, else: false
true

iex> if {:error, :embedded}, do: true, else: false
true

As you see in this example, it returns true even when there’s an error.

A better way to catch this is by using the ensure_compiled?/1 function.

Ensures the given module is compiled and loaded.
Similar to ensure_compiled/1, but returns true if the module is already loaded or was successfully loaded and compiled. Returns false otherwise.

So I tried to use this function and let my application compile again hoping that this was fixed now. My conclusion of using ensure_compiled?/1 is that the application will be compiled! :) Unfortunately @currencies was nil, because Poison wasn’t compiled before Currencies. I also received an warning because the @currencies attribute wasn’t set at compile time.

warning: undefined module attribute @currencies, please remove access to @currencies or explicitly set it before access lib/currencies.ex:59: Currencies.all/0

When using Currencies in an application, you should also have Poison in your dependencies. Otherwise the attribute @currencies won’t be set at compile time. This makes Currencies dependent on Poison.

Hopefully I explained this time better why this dependency should have Poison as an dependency. Thanks for creating this dependency ❤️

[coveralls]

Coverage remained the same at 100.0% when pulling 63087a9 on sjoulbak:feature/add-poison-dependency into 54cbaba on JakeStaTeresa:master.

[sjoulbak]

@JakeStaTeresa Would you please review this PR?

[sjoulbak]

@JakeStaTeresa Do you have any time to review this PR?

[JakeStaTeresa]

hi @sjoulbak! I saw a branch in your repo where you replaced ensure_compiled to ensure_compiled?. Did that change fix the issue for you? If yes can you send a PR from that branch?

[sjoulbak]

@JakeStaTeresa As I mentioned in my first comment:

So I tried to use this function and let my application compile again hoping that this was fixed now. My conclusion of using ensure_compiled?/1 is that the application will be compiled! :) Unfortunately @currencies was nil, because Poison wasn’t compiled before Currencies. I also received an warning because the @currenciesattribute wasn’t set at compile time.

warning: undefined module attribute @currencies, please remove access to @currencies or explicitly set it before access lib/currencies.ex:59: Currencies.all/0

When using Currencies in an application, you should also have Poison in your dependencies. Otherwise the attribute @currencies won’t be set at compile time. This makes Currencies dependent on Poison.