NestedFilter
The Problems
- You have a nested map (or a struct that you converted to a nested map) and you want to remove ALL the keys with specific values such as nil.
- You want to do a Map#take on a nested map
Example: Remove all the map keys with nil values
nested_map = %{a: 1, b: %{c: nil, d: nil}, c: nil}
Map.drop(nested_map, [:c, :d])
# => %{a: 1, b: %{c: nil, d: nil}}
# But you actually wanted:
# => %{a: 1}The Solution: NestedFilter
NestedFilter drills down into a nested map and can do any of the following:
- filters out keys according to user specified values.
- filters out values according to user specified keys.
Installation
If available in Hex, the package can be installed
by adding nested_filter to your list of dependencies in mix.exs:
def deps do
[{:nested_filter, "~> 1.2.2"}]
endDocumentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/nested_filter.
Usage
By default, when removing user specified values, empty values will be preserved (see Case 1 below). You can add empty values to the user specified values list if you wish those "empty values" (e.g., empty maps) to be removed.
NestedFilter.drop_by_value
# Case 1: Remove the nil values from a nested map, preserving empty map values
nested_map = %{a: 1, b: %{m: nil, n: 2}, c: %{p: %{q: nil, r: nil}, s: %{t: 2, u: 3}} }
NestedFilter.drop_by_value(nested_map, [nil])
# => %{a: 1, b: %{n: 2}, c: %{p: %{}, s: %{t: 2, u: 3}} }
# Case 2: Remove the nil values from a nested map, removing empty map values
nested_map = %{a: 1, b: %{m: nil, n: 2}, c: %{p: %{q: nil, r: nil}, s: %{t: 2, u: 3}} }
NestedFilter.drop_by_value(nested_map, [nil, %{}])
# => %{a: 1, b: %{n: 2}, c: %{s: %{t: 2, u: 3}} }NestedFilter.drop_by_key
# Case 1: Remove values from a nested map by key
nested_map = %{a: 1, b: %{a: 2, b: 3}, c: %{a: %{a: 1, b: 2}, b: 2, c: %{d: 1, e: 2}}}
assert NestedFilter.drop_by_key(nested_map, [:a]) == %{b: %{b: 3},c: %{b: 2, c: %{d: 1, e: 2}}}NestedFilter.take_by_key
# Case 1: Take values from a nested map by key
nested_map = %{a: %{b: 1}, c: 3, e: %{f: 4}}
assert NestedFilter.take_by_key(nested_map, [:b, :f]) == %{b: 1, f: 4 }You can browse the tests for more usage examples.