# `PB.Schema.Projection`
[🔗](https://github.com/hansihe/pb_ex/blob/v0.2.0/pb/lib/pb/schema/projection.ex#L1)

Compiled projection metadata attached to a message in the schema.

Projections drive message-level adapters, struct representations, identity
oneofs, and unwrapped single-field messages. The projection for a given
message is exposed on `%PB.Schema.Info.Message{}.projection`.

Projections are configured at compile time via the `:projections` option on
`PB.compile/2` and `use PB.Schema` (or in proto source via the
`elixir.pb.v1` custom options). The struct itself is the resolved,
post-merge form — callers should treat it as read-only.

# `t`

```elixir
@type t() :: %PB.Schema.Projection{
  adapter: PB.Adapter.t() | nil,
  extensions: :reject | {:field, atom()} | nil,
  oneofs: %{required(atom()) => :identity},
  preserved_unknown_fields: :drop | :reject | {:field, atom()} | nil,
  struct_mod: module() | nil,
  unwrap_field: atom() | nil
}
```

---

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