---
title: PredicateBindings
framework: foundation
role: symbol
role_heading: Structure
path: foundation/predicatebindings
---

# PredicateBindings

A mapping from a predicates’s input variables to their values.

## Declaration

```swift
struct PredicateBindings
```

## Overview

Overview If you define a custom predicate expression type, you must propagate the predicate’s bindings to its subexpressions. If you define a custom predicate type, you must create an instance of this structure, populate it with the predicate’s variables, and propagate it throughout the expression tree.

## Topics

### Initializers

- [init(_:)](foundation/predicatebindings/init(_:).md)

### Instance Methods

- [binding(_:to:)](foundation/predicatebindings/binding(_:to:).md)

### Subscripts

- [subscript(_:)](foundation/predicatebindings/subscript(_:).md)

## See Also

### Filltering

- [Predicate](foundation/predicate.md)
- [PredicateError](foundation/predicateerror.md)
- [PredicateCodableConfiguration](foundation/predicatecodableconfiguration.md)
- [PredicateCodableKeyPathProviding](foundation/predicatecodablekeypathproviding.md)
- [PredicateExpression](foundation/predicateexpression.md)
- [StandardPredicateExpression](foundation/standardpredicateexpression.md)
- [PredicateExpressions](foundation/predicateexpressions.md)
- [NSPredicate](foundation/nspredicate.md)
- [NSExpression](foundation/nsexpression.md)
- [NSComparisonPredicate](foundation/nscomparisonpredicate.md)
- [NSCompoundPredicate](foundation/nscompoundpredicate.md)