# LibTmux.Snapshot.require_field!/3

- **Module:** LibTmux
- **Package:** libtmux
- **Language:** Elixir
- **Kind:** function
- **Source:** https://github.com/libtmux/libtmux-elixir/blob/66b9b1c3f3f3186428abdfda2c76f5cf87446710/lib/libtmux/snapshot.ex#L245
- **Page:** https://libtmux.org/en/elixir/latest/reference/libtmux-snapshot-require_field-bang-3/

```
require_field!(snapshot, entity, field)
@spec require_field!(
        t(),
        LibTmux.Schema.entity_selector(),
        atom()
      ) :: :ok
```

Requires a loaded field over the captured entity domain before evaluation.

See the [worked example](api-examples.html#local-graph-and-filtering).

## Parameters

- `snapshot` (`t()`)
- `entity` (`LibTmux.Schema.entity_selector()`)
- `field` (`atom()`)