# ExPipeline
An opinionated library to build better pipelines.
## Creating a Pipeline
On the module that will implement the pipeline, simplye `use Pipeline` and you are ready to go.
- A function is considered a step if its name ends with `_step` and accepts exactly two parameters
- A function is considered a callback if its name ends with `_callback` and accepts exactly two parameters
- Steps and callbacks are executed in the order they are declared
- Steps must always return an ok/error tuple: `{:ok, value}` or `{:error, error}`
- If one step fails, following steps will not be executed
- Callbacks are always executed after all steps are called, regardless of the final result.
An example:
```elixir
defmodule MyModule do
use Pipeline
@doc """
First step of the pipeline
"""
def init_step(value, options) do
# {:ok, updated_value}
# or
# {:error, some_error}
end
@doc """
Second step of the pipeline
"""
def second_step(value, options) do
# {:ok, updated_value}
# or
# {:error, some_error}
end
@doc """
Callback - always executed, results ignored
"""
def report_callback(state, _options) do
MyReportingModule.publish(state)
end
end
```
With this module in place, you have two options to execute it:
- Calling the `execute/2` function from your module
- Calling the `execute/3` function from the `Pipeline` module
Both lines will execute the pipeline:
```elixir
MyModule.execute(starting_value, options)
Pipeline.execute(MyModule, starting_value, options)
```
## Installation
If [available in Hex](https://hex.pm/docs/publish), the package can be installed
by adding `ex_pipeline` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:ex_pipeline, "~> 0.1.0"}
]
end
```
