NSExpressionDescription

Inherits from
Conforms to
Framework
/System/Library/Frameworks/CoreData.framework
Availability
Available in OS X v10.6 and later.
Companion guide
Declared in
NSExpressionDescription.h

Overview

Instances of NSExpressionDescription objects represent a special property description type intended for use with the NSFetchRequest propertiesToFetch method.

An NSExpressionDescription describes a column to be returned from a fetch that may not appear directly as an attribute or relationship on an entity. Examples might include upper(attribute) or max(attribute). You cannot set an NSExpressionDescription object as a property of an entity.

Tasks

Getting Information About an Expression Description

Instance Methods

expression

Returns the expression for the receiver.

- (NSExpression *)expression
Return Value

The expression for the receiver.

Availability
  • Available in OS X v10.6 and later.
Declared In
NSExpressionDescription.h

expressionResultType

Returns the type of the receiver.

- (NSAttributeType)expressionResultType
Return Value

The type of the receiver.

Availability
  • Available in OS X v10.6 and later.
Declared In
NSExpressionDescription.h

setExpression:

Sets the expression for the receiver.

- (void)setExpression:(NSExpression *)expression
Parameters
expression

The expression for the receiver.

Special Considerations

This method raises an exception if the receiver’s model has been used by an object graph manager.

Availability
  • Available in OS X v10.6 and later.
Declared In
NSExpressionDescription.h

setExpressionResultType:

Sets the type of the receiver.

- (void)setExpressionResultType:(NSAttributeType)type
Parameters
type

An NSAttributeType constant that specifies the type for the receiver.

Special Considerations

This method raises an exception if the receiver’s model has been used by an object graph manager.

Availability
  • Available in OS X v10.6 and later.
Declared In
NSExpressionDescription.h