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# `useful`

A collection of useful functions for building `Elixir` Apps.

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# Why? 🤷

We found ourselves copy-pasting a few useful "helper" functions
across our Elixir projects ... <br />
it wasn't
["DRY"](https://en.wikipedia.org/wiki/Don%27t_repeat_yourself),
so we created this library.

# What? 💭

A library of useful functions 
that we reach for 
when building `Elixir` Apps.

# Who? 👤

This library is used in our various `Elixir` / `Phoenix` apps. <br />
As with everything we do it's Open Source, Tested and Documented
so that _anyone_ can benefit from it.

# How? 💻

## Install ⬇️

Install by adding `useful` to your list of dependencies in `mix.exs`:

```elixir
def deps do
  [
    {:useful, "~> 1.0.8"}
  ]
end
```

## Function Reference

### `atomize_map_keys/1`

Converts a `Map` that has strings as keys (or mixed keys)
to have only atom keys. e.g:

```elixir
# map that has different types of keys:
my_map = %{"name" => "Alex", id: 1}
Useful.atomize_map_keys(my_map)
%{name: Alex, id: 1}
```

Works recursively for deeply nested maps:

```elixir
person = %{"name" => "Alex", id: 1, details: %{"age" => 17, height: 185}}
Useful.atomize_map_keys(person)
%{name: Alex, id: 1, details: %{age: 17, height: 185}}
```

### `flatten_map/1`

Flatten a `Map` of any depth/nesting:

```elixir
iex> map = %{name: "alex", data: %{age: 17, height: 185}}
iex> Useful.flatten_map(map)
%{data__age: 17, data__height: 185, name: "alex"}
```

**Note**: `flatten_map/1` converts all Map keys to `Atom`
as it's easier to work with atoms as keys
e.g: `map.person__name` instead of `map["person__name"]`.
We use the `__` (_double underscore_)
as the delimiter for the keys of nested maps,
because if we attempt to use `.` (_period character_)
we get an error:

```elixir
iex(1)> :a.b
** (UndefinedFunctionError) function :a.b/0 is undefined (module :a is not available)
    :a.b()
```

### `stringify_tuple/1`

Stringify a tuple of any length; useful in debugging.

```elixir
iex> tuple = {:ok, :example}
iex> Useful.stringify_tuple(tuple)
"ok: example"
```

### `typeof/1`

Returns the type of a variable, e.g: "function" or "integer"
Inspired by
[**`typeof`**](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/typeof)
from `JavaScript` land.

```elixir
iex> myvar = 42
iex> Useful.typeof(myvar)
"integer"
```

### `empty_dir_contents/1`

Empties the directory 
(+deletes all files and any nested directories_)
recursively, but does _not_ delete the actual directory.
This is useful when you want to reset a directory,
e.g. when testing.

```elixir
iex> dir = "tmp" # contains lots of sub directories and files
iex> Useful.empty_dir_contents(dir)
{:ok, dir}
```

<br />

# Docs 📜

Detailed docs available at:
https://hexdocs.pm/useful/Useful.html

<br />

# Help Us Help You! 🙏

If you need a specific helper function or utility
(e.g: something you found useful in a different programming language),
please
[open an issue](https://github.com/dwyl/useful/issues)
so that we can all benefit from useful functions.

Thanks!