Elixir: Cheatsheet

We all love to cheat right? chill 😅, I mean using cheats to make our code simpler yet cooler. Here are some elixir cheats that I hope can help you code more effectively. I will also appreciate it if you have some corrections or other cheats that I can add here. Thanks!

1. Nil Catcher

UndefinedFunctionError
function nil.value/0 is undefined

Have you experienced this error? especially when trying to get a value 3 structs down to the main variable?ex: @music.singer.name, you can try this solution to never ever encounter this again.

Add this to your helper or base view:

def get(map, fields) when is_list(fields),
 do: Enum.reduce(fields, map, fn field, map -> if map, do: Map.get(map, field) end)

Or this:

def get(map, fields) when is_list(fields),
 do: Kernel.get_in(map, fields)
reference: Kernel.get_in/2

To use it, just do this:

<%= get(@music, ~w(singer name)a) %>

This will never return an UndefinedFunctionError

2. Shortened List Manipulations

data 
|> Enum.map(fn f -> %{name: f.name} end)
data
|> Enum.filter(fn f -> f.status == "active" end)
data 
|> Enum.find(fn f -> f.id == id end)

I’m sure you’ve tried using one of these code blocks and like me, I know you think that it’s kinda boring.

You can try this:

Not only that it became shorter removing fn f -> ... end , it became cooler to look at too.

data 
|> Enum.map(& %{name: &1.name } end)
data
|> Enum.filter(& &1.status == "active")
data 
|> Enum.find(& &1.id == sample_id)

Cool right ??? 😅

3. Shorthand Conditions

data = %{active: true}
if data.active do
  "Active"
else 
  "Not Active"
end
# Shorthand
if data.active, do: "Active", else: "Not Active"

Shorthand conditions depend on what you are doing inside your condition, if you’re doing a one-liner code, better use shorthand, but if not I suggest to do it the old-fashioned way.

You can also use this on your methods:

Instead of doing:
def is_active() do
...
end
You can try doing: 
def is_active(), do: ...

Example:

data = %{active: true}
def is_active(data) do
 if data.active do
  "Active"
 else 
  "Not Active"
 end
end
# The code above is not safe, if data is nil it will return an UndefinedFunctionError, You can use pattern matching with shorthand method:
def is_active(%{active: true}), do: "Active"
def is_active(_), do: "Not Active"
# Whats great here is that, no matter what type of value you pass on the method(list, nil or an atom), as long as it does not match the first method, it'll always go to the default method catcher, returning "Not Active".

4. Guards and Pattern Match

I think this is the coolest of them all, and personally, it made my code a little safer. But in case you already know this just skip.

data = %{name: "alvin"}
# This is a guard
def cool_method(data) when not is_nil(data), do: ...
def cool_method(_), do: ...
or 
# This is a pattern match
def cool_method(%{name: "alvin"}), do: ...
def cool_method(data), do: ...
# Combination of both
def cool_method(%{name: name} = data) when not is_nil(name), do: ...
def cool_method(_), do: ...

I can talk all day about guards and pattern matching but you’ll get bored so instead, you can check more here: guards and pattern match

If you find this helpful, I’d appreciate a coffee 😊