82 lines
2.9 KiB
Markdown
82 lines
2.9 KiB
Markdown
|
# Basketball Website
|
||
|
|
|
||
|
|
Welcome to Basketball Website 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
|
||
|
|
|
||
|
|
## Access Behaviour
|
||
|
|
|
||
|
|
Elixir uses code _Behaviours_ to provide common generic interfaces while facilitating specific implementations for each module which implements it. One such common example is the _Access Behaviour_.
|
||
|
|
|
||
|
|
The _Access Behaviour_ provides a common interface for retrieving data from a key-based data structure. The _Access Behaviour_ is implemented for maps and keyword lists, but let's look at its use for maps to get a feel for it. _Access Behaviour_ specifies that when you have a map, you may follow it with _square brackets_ and then use the key to retrieve the value associated with that key.
|
||
|
|
|
||
|
|
```elixir
|
||
|
|
# Suppose we have these two maps defined (note the difference in the key type)
|
||
|
|
my_map = %{key: "my value"}
|
||
|
|
your_map = %{"key" => "your value"}
|
||
|
|
|
||
|
|
# Obtain the value using the Access Behaviour
|
||
|
|
my_map[:key] == "my value"
|
||
|
|
your_map[:key] == nil
|
||
|
|
your_map["key"] == "your value"
|
||
|
|
```
|
||
|
|
|
||
|
|
If the key does not exist in the data structure, then `nil` is returned. This can be a source of unintended behavior, because it does not raise an error. Note that `nil` itself implements the Access Behaviour and always returns `nil` for any key.
|
||
|
|
|
||
|
|
## Instructions
|
||
|
|
|
||
|
|
You are working with a web development team to maintain a website for a local basketball team. The web development team is less familiar with Elixir and is asking for a function to be able to extract data from a series of nested maps to facilitate rapid development.
|
||
|
|
|
||
|
|
## 1. Extract data from a nested map structure
|
||
|
|
|
||
|
|
Implement the `extract_from_path/2` function to take two arguments:
|
||
|
|
|
||
|
|
- `data`: a nested map structure with data about the basketball team.
|
||
|
|
- `path`: a string consisting of period-delimited keys to obtain the value associated with the last key.
|
||
|
|
|
||
|
|
If the value or the key does not exist at any point in the path, `nil` should be returned
|
||
|
|
|
||
|
|
```elixir
|
||
|
|
data = %{
|
||
|
|
"team_mascot" => %{
|
||
|
|
"animal" => "bear",
|
||
|
|
"actor" => %{
|
||
|
|
"first_name" => "Noel"
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
BasketballWebsite.extract_from_path(data, "team_mascot.animal")
|
||
|
|
# => "bear"
|
||
|
|
BasketballWebsite.extract_from_path(data, "team_mascot.colors")
|
||
|
|
# => nil
|
||
|
|
```
|
||
|
|
|
||
|
|
Use the _Access Behaviour_ when implementing this function.
|
||
|
|
|
||
|
|
Do not use any `Map` or `Kernel` module functions for working with the nested map data structure.
|
||
|
|
|
||
|
|
## 2. Refactor using included functions
|
||
|
|
|
||
|
|
Your coworker reviewing your code tells you about a `Kernel` module function which does something very similar to your implementation.
|
||
|
|
|
||
|
|
Implement `get_in_path/2` to use this `Kernel` module function.
|
||
|
|
|
||
|
|
The arguments expected are the same as part 1.
|
||
|
|
|
||
|
|
```elixir
|
||
|
|
BasketballWebsite.get_in_path(data, "team_mascot.actor.first_name")
|
||
|
|
# => "Noel"
|
||
|
|
```
|
||
|
|
|
||
|
|
## Source
|
||
|
|
|
||
|
|
### Created by
|
||
|
|
|
||
|
|
- @neenjaw
|
||
|
|
|
||
|
|
### Contributed to by
|
||
|
|
|
||
|
|
- @angelikatyborska
|
||
|
|
- @NobbZ
|