# `GeoGenius.ResultMapper`
[🔗](https://github.com/agoodway/geo_genius/blob/main/lib/geo_genius/result_mapper.ex#L1)

Maps a `Postgrex.Result` into structs by column name.

`GeoGenius.AreaMatch` and `GeoGenius.ImportRun` both project a query result
with more than a dozen columns, several of them same-typed neighbours, into
their own struct. Both need the same rule -- map by column name, never by
position -- so it lives here once rather than as two copies that could
drift apart.

# `to_structs`

```elixir
@spec to_structs(Postgrex.Result.t(), %{optional(String.t()) => atom()}, module()) ::
  [struct()]
```

Maps a query result into structs of `module`, using `fields` to translate
column names to struct keys.

Mapping is by column name rather than position. Both projections that use
this declare more than a dozen columns with several same-typed neighbours,
so a positional mapping would transpose two of them silently the first time
a projection changed.

Raises if a column in the result has no entry in `fields`: an unmapped
column is a projection bug to fix, not a value to drop silently.

---

*Consult [api-reference.md](api-reference.md) for complete listing*