Question: Being new to Elixir I'm having some problems understanding pattern matching.

If I have an Elixir data structure like this:

```
list_with_maps = [%{"id" => 1, "name" => "a"}, %{"id" => 2, "name" => "b"}]

```

What would be the best way to get values of all id fields from it?

Answer: 
You can map over the list and return the id using [Enum.map/2](http://elixir-lang.org/docs/v1.1/elixir/Enum.html#map/2)

```
Enum.map(list_with_maps, fn (x) -> x["id"] end)
[1, 2]

```

You can write the same function using the [capture](http://elixir-lang.org/docs/v1.1/elixir/Kernel.SpecialForms.html#&/1) operator:

```
Enum.map(list_with_maps, & &1["id"])

```

I prefer writing `& &1["id"]` as `&(&1["id"])` but the parentheses are optional.
A more generic (and simpler) way of getting a subset of the keys of a `Map` is to use `Map.take/2`, which you can use like this:

```
map = %{"id" => 1, "name" => "a"}
Map.take(map, ["id"])
> %{"id" => 1}

```

As you can see, it takes an array of keys and returns a new map with only the keys you want.

Now, applying this to a list is as simple as using a map, and then using the `Map.take/2` in mapper function. As has been pointed out, you can do this using either a lambda:

```
Enum.map(list_with_maps, fn (map) -> Map.take(map, ["id"]) end)

```

Or you can use a capture:

```
Enum.map(list_with_maps, &(Map.take(&1, ["id"])))

```

This will create more intermediate maps, but for most situations that won't be a problem, as Elixir is pretty smart about memory re-usage and won't actually create these objects a lot of the times, unles