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: ×_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