Usage Guide

Once Shapt is one of his dependencies. You gonna need to create a feature toggle module:

defmodule TestModule do
  use Shapt,
    adapter: [
      prod: {Shapt.Adapters.Env, []}
    ],
    toggles: [
      feature_x?: %{
        force: true,
        key: "MYAPP_FEATURE_X",
        deadline: ~D[2019-12-31]
      },
      feature_y?: %{
        deadline: ~D[2009-12-31]
      }
    ]
end

This module is a worker that you need to add to your supervision tree. Shapt will create the proper child_spec/1 and start_link/1 functions.

Options

• adapter: receives a keyword list of adapters by environment.
• toggles: receives a keyword list of toggles to be configured.

Default configurations

If no adapter is provided Shapt gonna set by default, Shapt.Adapters.Env as the production adapter and Shapt.Adapters.DotEnv as develompment and test adapter. toggles option has no default values.

Provided functions

Just by using Shapt you gonna have some extra functions on your feature toggle module:

key_name/0

For each key in the toggles option keyword list you gonna have a fucntion that represents that feature toggle. From the example above you would have in TestModule the functions feature_x?/0 and feature_y?/0, those functions always return only true or false.

toggle/2

Besides the key named functions you gonna have toggle/2. It can be used to evaluate the feature toggle and what to do when it's on or off. Some usage examples:

# just returning values
TestModule.toggle(:feature_x?, on: FeatureX, off: OldFeature)

# applying functions that receive the same parameters
TestModule.toggle(:feature_x?, env: [params, options], on: &Feature.x/2, off: &Feature.old/2)

# applying functions with different parameters:
TestModule.toggle(:feature_x?, on: {ModuleX, :function, [paramsx]}, off: {Module, :fuction, [params]})

In those two last examples we use the apply function, be aware of that when using this feature. So make sure that the env or the third element tuple is always a list which the size is the same as the provided function arity.

expired?/1

It receives the name of a toggle and says if it's expired or not.

enabled?/1

It receives the name of a toggle and says if it's enabled or not.

expired_toggles/0

List all expired toggles

output_template/0

Return the binary representing the template file generated by the Adapter.

instance_name/0

By default instance_name/0 will always return nil. This function is overridable so when needed you can specified the behavior to determine which instance we are running. For the default Adapters provided here this function has no utility, but it gonna be useful for future Adapters.

Env Adapter

Shapt.Adapters.Env will work directly with environment variables using the System.get_env/1. This is why the adapter doesn't receive any configuration.

DotEnv Adapter

Shapt.Adapters.DotEnv works with a .env file. If no option is provided it gonna try to read a .env file from the root of the mix project you're running. To provide a file you can set {Shapt.Adapters.DotEnv, [file: "path/to/file.env"]} on your adapter configuration.

Testing

Shapt is built having in mind that you probably gonna use Mox to write tests. By using Mox you only need mock enabled?/2 callback. You can have more info on Shapt.Adapter behaviour docs.