exercism/elixir/community-garden

Community Garden

Welcome to Community Garden on Exercism's Elixir Track. If you need help running the tests or submitting your code, check out HELP.md. If you get stuck on the exercise, check out HINTS.md, but try and solve it without using those first :)

Introduction

Agent

The Agent module facilitates an abstraction for spawning processes and the receive-send loop. From here, we will call processes started using the Agent module 'agent processes'. An agent process might be chosen to represent a central shared state.

To start an agent process, Agent provides the start/2 function. The supplied function when start-ing the agent process returns the initial state of the process:

# Start an agent process with an initial value of an empty list
{:ok, agent_pid} = Agent.start(fn -> [] end)

Just like Map or List, Agent provides many functions for working with agent processes.

It is customary to organize and encapsulate all Agent-related functionality into a module for the domain being modeled.

Instructions

Your community association has asked you to implement a simple registry application to manage the community garden registrations. The Plot struct has already been provided for you.

1. Open the garden

Implement the CommunityGarden.start/1 function, it should receive an optional keyword list of options to pass forward to the agent process. The garden's initial state should be initialized to represent an empty collection of plots. It should return an :ok tuple with the garden's pid.

{:ok, pid} = CommunityGarden.start()
# => {:ok, #PID<0.112.0>}

2. List the registrations

Implement the CommunityGarden.list_registrations/1 function. It should receive the pid for the community garden. It should return a list of the stored plots that are registered.

CommunityGarden.list_registrations(pid)
# => []

At this point, we haven't added the ability to register a plot, so this list should be empty

3. Register plots to a person

Implement the CommunityGarden.register/2 function. It should receive the pid for the community garden and a name to register the plot. It should return the Plot struct with the plot's id and person registered to when it is successful.

The ids should be incremental and unique. You can keep an id counter in the agent's state.

CommunityGarden.register(pid, "Emma Balan")
# => %Plot{plot_id: 1, registered_to: "Emma Balan"}
CommunityGarden.list_registrations(pid)
# => [%Plot{plot_id: 1, registered_to: "Emma Balan"}]

4. Release plots

Implement the CommunityGarden.release/2 function. It should receive the pid and id of the plot to be released. It should return :ok on success. When a plot is released, the id is not re-used, it is used as a unique identifier only.

CommunityGarden.release(pid, 1)
# => :ok
CommunityGarden.list_registrations(pid)
# => []

5. Get a registered plot

Implement the CommunityGarden.get_registration/2 function. It should receive the pid and id of the plot to be checked. It should return the plot if it is registered, and :not_found if it is unregistered.

CommunityGarden.get_registration(pid, 1)
# => %Plot{plot_id: 1, registered_to: "Emma Balan"}
CommunityGarden.get_registration(pid, 7)
# => {:not_found, "plot is unregistered"}

Source

Created by

• @neenjaw

Contributed to by

• @angelikatyborska
• @jrr
• @efx
• @justin-m-morgan
• @cr0t