Keyword.get_lazy

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get_lazy(keywords, key, fun)

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Specs

get_lazy(t(), key(), (() -> value())) :: value()

Gets the value for a specific key.

If key does not exist, lazily evaluates fun and returns its result.

This is useful if the default value is very expensive to calculate or generally difficult to setup and teardown again.

If duplicated entries exist, the first one is returned. Use get_values/2 to retrieve all entries.

Examples

iex> keyword = [a: 1]
iex> fun = fn ->
...>   # some expensive operation here
...>   13
...> end
iex> Keyword.get_lazy(keyword, :a, fun)
1
iex> Keyword.get_lazy(keyword, :b, fun)
13