PATH  Documentation > WebObjects 4.5 > EOControl Reference

Table of Contents

EONullValue


Inherits from:
(com.apple.client.eocontrol) Object
(com.apple.yellow.eocontrol) NSObject
Implements:
(com.apple.client.eocontrol only) NSCoding
(com.apple.client.eocontrol only) EOSortOrdering.Comparison
(com.apple.client.eocontrol only) Cloneable
Package:
com.apple.client.eocontrol
com.apple.yellow.eocontrol


Class Description


The EONullValue class defines a unique object used to represent null values in collection objects (which don't allow null values). For example, NSDictionaries fetched by an EOAdaptorChannel contain an EONullValue instance for such values. EONullValue is automatically translated to null in enterprise objects, however, so most applications should rarely need to account for this class.

EONullValue has exactly one instance, returned by the nullValue static method. You can safely cache this instance and use the == operator to test for the presence of a null value:

EONullValue myNull = EONullValue.nullValue();
/* ... */
if (value == myNull) {
    /* ... */
}




Interfaces Implemented


NSCoding (com.apple.client.eocontrol only)
classForCoder
encodeWithCoder
EOSortOrderingComparison
compareAscending
compareCaseInsensitiveAscending
compareCaseInsensitiveDescending
compareDescending
Cloneable (com.apple.client.eocontrol only)


Constructors



EONullValue

public EONullValue()

Returns the unique instance of EONullValue.


Static Methods



nullValue

public static EONullValue nullValue()

Returns the unique instance of EONullValue.


Table of Contents