EOGenericRecord

Inherits from:
EOCustomObject

Package:
com.webobjects.eocontrol

Class Description

EOGenericRecord is a generic enterprise object class that can be used in place of custom classes when you don't need custom behavior. It implements the EOEnterpriseObject interface to provide the basic enterprise object behavior. An EOGenericRecord object has an EOClassDescription that provides metadata about the generic record, including the name of the entity that the generic record represents and the names of the record's attributes and relationships. A generic record stores its properties in a dictionary using its attribute and relationship names as keys.

In the typical case of applications that access a relational database, the access layer's modeling objects are an important part of how generic records map to database rows: If an EOModel doesn't have a custom enterprise object class defined for a particular entity, an EODatabaseChannel using that model creates EOGenericRecords when fetching objects for that entity from the database server. During this process, the EODatabaseChannel also sets each generic record's class description to an EOEntityClassDescription, providing the link to the record's associated modeling objects. (EOModel, EODatabaseChannel, and EOEntityClassDescription are defined in EOAccess.)

Creating an Instance of EOGenericRecord

The best way to create an instance of EOGenericRecord is using the EOClassDescription method createInstanceWithEditingContext as follows:


EOEnterpriseObject newEO;
String entityName;       // Assume this exists.

EOClassDescription description = 
    ClassDescription.classDescriptionForEntityName(entityName);
newEO = description.createInstanceWithEditingContext(null, null);

createInstanceWithEditingContext is preferable to using the constructor because the same code works if you later use a custom enterprise object class instead of EOGenericRecord. You can get an EOClassDescription for an entity name as shown above. Alternatively, you can get an EOClassDescription for a destination key of an existing enterprise object as follows:


EOEnterpriseObject newEO;
EOEnterpriseObject existingEO;   // Assume this exists.
String relationshipName;       // Assume this exists.
EOClassDescription sourceDesc = existingEO.classDescription();
EOClassDescription desc =     sourceDesc.classDescriptionForDestinationKey(relationshipName);

newEO = desc.createInstanceWithEditingContext(null, null);

The technique in this example is useful for inserting a new destination object into an existing enterprise object-for creating a new Movie object to add to a Studio's array of Movies, for example.

Constructors

EOGenericRecord

public EOGenericRecord( EOEditingContext anEditingContext, EOClassDescription aClassDescription, EOGlobalID globalID)

Creates a new EOGenericRecord. The new EOGenericRecord gets its metadata from aClassDescription. You should pass null for anEditingContext and globalID, because the arguments are optional: EOGenericRecord's implementation does nothing with them. Throws an exception if aClassDescription is null.

You shouldn't use these constructors to create new EOGenericRecords. Rather, use EOClassDescription's createInstanceWithEditingContext method. See the class description for more information.

public EOGenericRecord()

Description forthcoming.

public EOGenericRecord(EOClassDescription classDescription)

Description forthcoming.

Static Methods

usesDeferredFaultCreation

public static boolean usesDeferredFaultCreation()

Returns true, specifying that EOGenericRecords use deferred faulting (which is more efficient than the regular faulting mechanism.)

Instance Methods

classDescription

public EOClassDescription classDescription()

Description forthcoming.

storedValueForKey

public abstract Object storedValueForKey(String key)

Overrides the default implementation to simply invoke valueForKey.

See Also: storedValueForKey (EOKeyValueCoding)

takeStoredValueForKey

public abstract void takeStoredValueForKey( Object value, String key)

Overrides the default implementation to simply invoke takeValueForKey.

See Also: takeStoredValueForKey (EOKeyValueCoding)

takeValueForKey

public void takeValueForKey( Object value, String key)

Invokes the receiver's willChange method, and sets the value for the property identified by key to value. If value is null, this method removes the receiver's dictionary entry for key. (EOGenericRecord overrides the default implementation.) If key is not one of the receiver's attribute or relationship names, EOGenericRecord's implementation does not invoke handleTakeValueForUnboundKey. Instead, EOGenericRecord's implementation does nothing.

valueForKey

public Object valueForKey(String key)

Returns the value for the property identified by key. (EOGenericRecord overrides the default implementation.) If key is not one of the receiver's attribute or relationship names, EOGenericRecord's implementation does not invoke handleQueryWithUnboundKey. Instead, EOGenericRecord's implementation simply returns null. This method calls willRead.