ExMapper

Defining non trivial transformations from incoming maps to Structs.

#Quick example

  defmodule Bar do
    use ExMapper.DefMapping
    defstruct [:baz]

    defmapping do
      override :baz, key: &string_key_prefix/1, value: &times_two/1
    end

    defp times_two(input), do: input * 2
    defp string_key_prefix(key), do: "KEY_#{key}"

  end


  defmodule Foo do
    use ExMapper.DefMapping
    defstruct [:bar, :a]

    defmapping do
      keys: :atomized
      override :bar, value: one(%Bar{}, Bar.mappings)
    end
  end

Then:

  ExMapper.map(%Foo{}, input, Foo.mappings)

Usage

To define a mapping use the ExMapper.DefMapping DSL and the defmapping macro. The result is the module will have a mappings function which you can pass to ExMapper.

Once in a defmapping block, two macros are avaliable for you:

• keys/1 takes either an atom [:atomized|:stringified] which will tell the mapper to look in the input for matching keys of either string or atom type. Or, you can provide a function in the format struct_key -> expected_key
• overrides/2 - takes the struct key and Options

Override options can include:

• key: either a string/atom value to query the input map. Or similarly with the overall keys definition you can specify a function in the format struct_key -> expected_key
• value: either a string/atom value to use despite whats in the input map. Or more useful a function in the format input_value -> transformed_value

Notes

• Mappings and structs do not, and really should not be in the same module if you have several mapping definitions for a struct
• Helper functions one and many allow mapping to nested Structs