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# NSExpression.ExpressionType

Defines the possible types of an expression.

```
enum ExpressionType
```

## Topics

### Constants

[`NSConstantValueExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/constantValue)

An expression that always returns the same value.

[`NSEvaluatedObjectExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/evaluatedObject)

An expression that always returns the parameter object itself.

[`NSVariableExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/variable)

An expression that always returns whatever value is associated with the key specified by ‘variable’ in the bindings dictionary.

[`NSKeyPathExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/keyPath)

An expression that returns something that can be used as a key path.

[`NSFunctionExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/function)

An expression that returns the result of evaluating a function.

[`NSUnionSetExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/unionSet)

An expression that creates a union of the results of two nested expressions.

[`NSIntersectSetExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/intersectSet)

An expression that creates an intersection of the results of two nested expressions.

[`NSMinusSetExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/minusSet)

An expression that combines two nested expression results by set subtraction.

[`NSSubqueryExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/subquery)

An expression that filters a collection using a subpredicate.

[`NSAggregateExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/aggregate)

An expression that defines an aggregate of `NSExpression` objects.

[`NSAnyKeyExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/anyKey)

An expression that represents any key.

[`NSBlockExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/block)

An expression that uses a Block.

[`NSConditionalExpressionType`](/documentation/Foundation/NSExpression/ExpressionType-swift.enum/conditional)

A conditional expression that evaluates a predicate to determine which expression to return.

## Relationships

### Conforms To

[`Equatable`](/documentation/Swift/Equatable)

[`RawRepresentable`](/documentation/Swift/RawRepresentable)

[`Hashable`](/documentation/Swift/Hashable)

[`BitwiseCopyable`](/documentation/Swift/BitwiseCopyable)

[`Sendable`](/documentation/Swift/Sendable)

[`SendableMetatype`](/documentation/Swift/SendableMetatype)

---

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