PATH Documentation > WebObjects 4.5 > EOAccess Reference

EOModelGroup

Inherits from: NSObject

Conforms to: NSObject
(NSObject)

Declared in: EOAccess/EOModelGroup.h

Class Description

An EOModelGroup represents an aggregation of related models (see the EOModel class specification for more information on models). When a model in the group needs to resolve a relationship to an entity in another model, it looks for that model in its group. Model groups allow applications to load entities and their properties only as they're needed, by distributing them among separate EOModels.

The default model group contains all models for an application, as well as any frameworks the application references. It is automatically created on demand. The entity name space among all of these models is global; consequently, the same entity name shouldn't appear in any two of the models. All cross-model information is represented in the models by entity name only. Binding the entity name to an actual entity is done at run-time within the EOModelGroup.

In the majority of applications, the automatic creation of the default model group is sufficient. However, your code can override this automatic creation; see "Setting Up A Model Group Programmatically" .

Accessing Models Within a Model Group

Each model lives within a group and can form connections to other models in its group. A model can find a related model using the statement:

[[self modelGroup] modelNamed:name];

A data source can locate a model using the statement:

[[EOModelGroup defaultGroup] modelNamed:name];

EOModeler puts models with identical names in separate groups to allow you to load two models with the same name at the same time.

EOModelGroup Delegates

Your EOModelGroup object should have a delegate which can influence how it finds and loads models. In addition to the delegates you assign to EOModelGroup instances, the EOModelGroup class itself can have a delegate. The class delegate implements a single method- defaultModelGroup-while the instance delegate can implement the methods defined in the EOModelGroup Delegate protocol. For more information on EOModelGroup class delegate and instance delegate methods, see the EOModelGroup Class Delegate and EOModelGroup Delegate protocol specifications, respectively. Note that the following delegate methods are set on EOModelGroup, rather than EOEntity, to provide a single point in the code where you can alter the database-to-objects mapping:

Constants

In EOModelGroup.h, EOModelGroupEOAccess defines NSString constants for the names of the notifications it posts. For more information on these notifications, see "Notifications" .

Method Types

Accessing models

- addModelWithFile:

- modelNamed:

- modelNames

- models

- modelWithPath:

- removeModel:

Accessing model groups

+ defaultGroup

+ setDefaultGroup:

+ globalModelGroup

Searching a group

- entityNamed:

- entityForObject:

- entitiesWithSharedObjects

- fetchSpecificationNamed:entityNamed:

- storedProcedureNamed:

Loading all of a group's objects

- loadAllModelObjects

Assigning a delegate

+ classDelegate

- delegate

+ setClassDelegate:

- setClassDelegate:

Class Methods

classDelegate

+ (id)classDelegate

Returns the EOModelGroup's class delegate. This delegate optionally implements the defaultModelGroup method (see the EOModelGroup Class Delegate protocol specification for more information).

See Also: + setClassDelegate:

defaultGroup

+ (EOModelGroup *)defaultGroup

Returns the default EOModelGroup. Unless you've either specified a default model group with setDefaultGroup: or implemented the defaultModelGroup class delegate method to return a non-nil value, this method is equivalent to globalModelGroup.

See Also: + classDelegate

globalModelGroup

+ (EOModelGroup *)globalModelGroup

Returns an EOModelGroup composed of all models in the resource directory of the main bundle, as well as those in all the bundles and frameworks loaded into the application.

See Also: + defaultGroup

setClassDelegate:

+ (void)setClassDelegate:(id)anObject

Assigns anObject as the EOModelGroup's class delegate. The class delegate is optional; it allows you to determine the default model group (see the EOModelGroup Class Delegate protocol specification for more information).

See Also: + classDelegate, - defaultModelGroup

setDefaultGroup:

+ (void)setDefaultGroup:(EOModelGroup *)group

Sets the default model group to group. If you've implemented the defaultModelGroup class delegate method to return a non-nil value, the delegate's return value overrides group as the default model group.

See Also: + defaultGroup, + setClassDelegate:

Instance Methods

addModel:

- (void)addModel:(EOModel *)model

Adds a model to the receiver, sets the model's model group to the receiver, and posts EOModelAddedNotification. Raises an exception if the receiver already contains an EOModel with the same name as the specified model.

addModelWithFile:

- (EOModel *)addModelWithFile:(NSString *)path

Creates an EOModel object with the contents of the file identified by path, adds the newly-created model to the receiver, and returns it. Throws an exception if for any reason it cannot create the model from the file specified by path. Uses the EOModel method initWithContentsOfFile: to initialize the new model, and adds it to the receiver.

delegate

- (id)delegate

Returns the receiver's delegate, which is different from the EOModelGroup's class delegate. Each EOModelGroup object can have it's own delegate in addition to the delegate that's assigned to the EOModelGroup class. See the EOModelGroup Delegate protocol specification for more information.

See Also: - setClassDelegate:, + classDelegate

entitiesWithSharedObjects

- (NSArray *)entitiesWithSharedObjects

Returns an array of entities that have objects to load into a shared editing context.

entityForObject:

- (EOEntity *)entityForObject:(id)object

Returns the EOEntity associated with object from any of the models in the receiver that handle object, or nil if none of the entities in the receiver handles object.

See Also: - entityForObject: (EOModel)

entityNamed:

- (EOEntity *)entityNamed:(NSString *)entityName

Searches each of the EOModels in the receiver for the entity specified by entityName, and returns the entity if found. Returns nil if it is unable to find the specified entity.

See Also: - entityNamed: (EOModel)

fetchSpecificationNamed:entityNamed:

- (EOFetchSpecification *)fetchSpecificationNamed:(NSString *)fetchSpecName entityNamed:(NSString *)entityName

Returns the named fetch specification from the entity specified by entityName in the receiving model group.

loadAllModelObjects

- (void)loadAllModelObjects

Sends loadAllModelObjects to each of the receiver's EOModels, thereby loading any EOEntities, EOAttributes, EORelationships, and EOStoredProcedures that haven't yet been loaded from each of the EOModels in the receiver.

See Also: - loadAllModelObjects (EOModel)

modelNamed:

- (EOModel *)modelNamed:(NSString *)modelName

Returns the EOModel named modelName if it's part of the receiver, or nil if the receiver doesn't contain an EOModel with the specified name.

modelNames

- (NSArray *)modelNames

Returns an array containing the names of all of the EOModels in the receiver, or an empty array if the receiver contains no EOModels. The order of the model names in the array isn't defined.

models

- (NSArray *)models

Returns an array containing the receiver's EOModels, or an empty array if the receiver contains no EOModels. The order of the models in the array isn't defined.

modelWithPath:

- (EOModel *)modelWithPath:(NSString *)path

If the receiver contains an EOModel whose path (as determined by sending path to the EOModel object) is equal to path, that EOModel is returned. Otherwise, returns nil. NSString's isEqual: method is used to compare the paths, and each path is standardized (with stringByStandardizingPath) before comparison.

See Also: - path (EOModel)

removeModel:

- (void)removeModel:(EOModel *)aModel

Removes aModel from the receiver, and unbinds any connections to aModel from other EOModels in the receiver. Posts EOModelInvalidatedNotification to the default notification center after removing aModel from the receiver.

See Also: - EOModelGroup, - models

setDelegate:

- (void)setDelegate:(id)anObject

Sets the receiver's delegate to anObject. See the EOModelGroup Delegate protocol specification for more information.

See Also: - delegate

storedProcedureNamed:

- (EOStoredProcedure *)storedProcedureNamed:(NSString *)aName

Returns the stored procedure in the receiving model group having the given name.

Notifications

EOModelGroup declares and posts the following notifications.

EOModelAddedNotification

Posted by an EOModelGroup when an EOModel is added to the group. This notification is sent, for instance, inside Interface Builder when the user has saved changes to a model in EOModeler and the objects in Interface Builder must be brought back in sync. The old model is flushed and receivers of the notification (like data sources) can invoke modelNamed: to re-fetch their models.

Notification Object	The newly added model.
Userinfo	None

EOModelInvalidatedNotification

Posted by an EOModelGroup when an EOModel is removed from the group. This notification is sent, for instance, inside Interface Builder when the user has saved changes to a model in EOModeler and the objects in Interface Builder must be brought back in sync. The old model is flushed and receivers of the notification (like data sources) can invoke modelNamed: to re-fetch their models.

Notification Object	The invalidated model.
Userinfo	None