# FilterExpr.where(_:_:)

- **Module:** FilterExpr
- **Package:** libtmux-swift
- **Language:** Swift
- **Kind:** method
- **Source:** https://github.com/libtmux/libtmux-swift/blob/f02a4668570e1cc5198c941413750e021f42c214/Sources/LibTmux/FilterExpr.swift#L173
- **Page:** https://libtmux.org/reference/swift/filterexpr-where(_-_-)/

```
FilterExpr.where(_:_:)(keyPath: KeyPath<Root, Value> & Sendable, operation: FilterOperator<Value>) -> FilterExpr<Root>
```

Builds a comparison from a key path.

The key path is lowered to a stable field id here and then discarded —
nothing downstream holds one, so an expression can cross a boundary a
key path could not.

## Raises

- `QueryConstructionError`