Elixir map check if not empty and key exists
Gazeler's answer is obviously really good. I would only add pattern matching to the mix, as it seems to me, that's the clearest solution, that works not only with phoenix, but with any map anywhere in Elixir.
# head-only declaration for default params
def changeset(model, params \\ :empty)
def changeset(model, %{"username" => _} = params) do
# username field is in params
end
def changeset(model, params) do
# username is not in params
end
Just a small terminology thing, params is a map and not a hash. This is relevant when knowing where to look in the documentation.
For a map there is has_key?/2 which returns true
or false
.
Map.has_key?(params, :name)
Since you are using an Ecto changeset then you can also use Ecto.Changeset.get_change/3.
get_change(changeset, key, default \\ nil)
This returns default
if key
is not set. Please note that if key
is set to nil
then nil
will still be returned. If nil
is a permitted value for your change then you may want to set a different default parameter.