Legacy Document
Important: The information in this document is obsolete and should not be used for new development.
The Model Browser for Data Modeling
The data modeling tool browser’s three parts are the entities pane, the properties or fetch requests pane, and the detail pane. The detail pane itself has three separate views: the General pane, the User Info pane, and the Configurations pane.
In this section:
The Entities Pane
The Properties Pane
The Detail Pane
The Entities Pane
The table in the entities pane lists all the entities in the model, either as a flat list or in an inheritance hierarchy. The table has three columns, showing the entity name, the class used to represent the entity, and a checkbox that indicates whether the entity is abstract.
You can edit the entity and class names directly in the text field cells—double click the text to make it editable—and toggle the abstract setting of an entity by clicking the checkbox.
To add a new entity to the model, you click the plus sign to the left of the horizontal scroll bar, or choose Design > Data Model > Add Entity. You delete a selected entity or selected entities by clicking on the minus sign, or by pressing the Delete key.
The Properties Pane
The table in the properties pane lists the properties or fetch requests associated with the selected entities. You choose what features you want to view by choosing from the pop-up menu available from the button with the “v” to the left of the horizontal scroll bar, as shown in Figure 12-3.
Note that the properties table shows the set of all properties of all entities selected in the entities table. Moreover, you can select and edit multiple properties at the same time. If several entities have a similar property, you can change them all simultaneously if you wish.
Properties View
The properties table has five columns showing the name of the property, a checkbox that indicates whether the property is optional, a checkbox that indicates whether the property is transient, the kind of property (attribute, relationship, or fetched), and the type (for example, date or integer if the property is an attribute) or destination entity (if the property is a relationship) of the property (see Figure 12-4).
You can edit most property values directly in the properties table—the exception is the property type (“Kind”) which you specify when you first add the property. You typically edit the predicate associated with fetched properties from the detail pane, using the predicate builder(see “The Predicate Builder”).
You add new properties using the pop-up menu from the plus sign to the left of the horizontal scroll bar (as shown in Figure 12-5), or by using the Design > Data Model menu. From the pop-up menu, you choose what sort of property you want to add—an attribute, a relationship, or a fetched property.
Fetch Requests View
The fetch requests view displays the fetch requests associated with an entity as shown in Figure 12-6. You add fetch requests using the plus sign button. You can edit the name of the fetch request and the predicate directly in the table view; however you typically construct the predicate graphically using the predicate builder from the detail pane.
When you add a fetch request to an entity, you are specifying that that entity is the one against which the fetch will be performed. For example, if you add a fetch request called “comedies” to the Movie entity, in code you would retrieve it from the model using:
NSFetchRequest *fetchRequest = [managedObjectModel |
fetchRequestTemplateForName:@"comedies"]; |
The returned fetch request’s entity is set to Movie. Since fetch requests are nevertheless general to the model, fetch request names must be unique across all entities. If you try to set a duplicate name, you get a warning sheet and you must choose a unique name before you can proceed.
The Detail Pane
The detail pane itself has three panes, the General pane, the User Info pane, and the Configurations pane. You choose which pane to display by clicking on the corresponding element in the segmented control in the upper right of the pane, shown in Figure 12-7.
General Pane
The general pane is different for entities, attributes (and for different types of attribute), relationships, and fetch requests. It changes automatically to the appropriate view depending on the last selection. Each view shows, and allows you to edit, details of the selected element.
For entities, you can edit the entity name, the name of the class used to represent the entity, and the parent entity, and you can specify whether or not the entity is abstract.
For attributes, you can specify the name and type, and whether it is optional or transient. When you specify the type, the pane updates to allow you to specify various constraints on the values the attribute may take. For example, for numeric and date attributes you can specify maximum, minimum, and default values, and for string attributes you can specify maximum and minimum length, a default value, and a regular expression that the string must match.
For relationships, you can specify the name, cardinality, and destination of the relationship. You can also specify a delete rule, and—for to-many relationships—maximum and minimum counts.
For fetched properties, you specify the name, the destination entity, and the predicate to be used for the fetch. You edit the predicate using the predicate builder by clicking the Edit Predicate button. For more details about the predicate builder, see “The Predicate Builder.”
For fetch requests, you specify the name and the predicate. As with fetched properties, you edit the predicate using the predicate builder by clicking the Edit Predicate button—see “The Predicate Builder.”
User Info Pane
The user info pane shows the info dictionary associated with the currently selected model element. Most elements in the model (entities, attributes, and relationships, but not fetch requests) may have an associated info dictionary that you can retrieve at runtime. The dictionary comprises key-value pairs. Using the info dictionary pane, you can specify any keys and string values you wish that may be of use in your application.
Configurations Pane
A configuration is a named collection of entities in the model. The configuration pane (show in Figure 12-8) therefore applies only to entities. You use it to add and remove configurations and to associate entities with configurations.
A model may have an arbitrary number of configurations. You add configurations using the plus sign button. Configurations appear in the list for all entities. The checkbox specifies whether or not the currently selected entity is associated with the given configuration.
Last updated: 2006-11-07
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