Pattern Matching and Updating Maps
The question we most often ask of our maps is, “Do you have the following keys (and maybe values)?”
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Is there an entry with the key :name?
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Are there entries for the keys :name and :height?
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Does the entry with key :name have the value "Dave"?
Here’s how we ask these questions using Elixir patterns.
| | iex> person = %{ name: "Dave", height: 1.88 } |
| | %{height: 1.88, name: "Dave"} |
| | iex> %{ name: a_name } = person |
| | %{height: 1.88, name: "Dave"} |
| | iex> a_name |
| | "Dave" |
| | iex> %{ name: _, height: _ } = person |
| | %{height: 1.88, name: "Dave"} |
| | iex> %{ name: "Dave" } = person |
| | %{height: 1.88, name: "Dave"} |
Our map does not have the key :weight, so the following pattern match fails:
| | iex> %{ ... |
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