TAILIEUCHUNG - Phát triển ứng dụng cho iPhone và iPad - part 19

Tham khảo tài liệu 'phát triển ứng dụng cho iphone và ipad - part 19', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Modeling Your Data 149 Services is beyond the scope of this book but if you want more information on using Sync Services refer to the Apple Sync Services Programming Guide available at http mac library documentation cocoa Conceptual SyncServices . Adding Attributes Now that you have created the Product entity you need to add the attributes of the entity. The Product should have the attributes defined in the Entity-Relationship Diagram as shown previously in Figure 6-2. Select the Product entity in the data model. With the entity selected click the plus icon at the bottom of the Properties pane. A pop-up menu opens allowing you to add various properties to the Product entity. Select Add Attribute from this pop-up menu to add a new attribute to the entity. The Detail pane tabs that are available when you select an attribute are slightly different from those available when you select an entity as you can see in Figure 6-5. The General tab in the Detail pane allows you to define the name and type of your attribute. Change the name of the attribute that you just added to name. You will store the name of the product in this attribute. Change the type of the name attribute to String. FIGURE 6-5 Attribute detail tabs Depending on the data type that you select for your attribute the dialog will display different fields that allow you to set additional options for the attribute. For the numeric types Integer 16 Integer 32 Integer 64 Decimal Double Float and Date the pane allows you to enter minimum and maximum values to use for validation. If the user attempts to save an entity with a value that is outside of the specified range Core Data will raise an error to notify you that a validation rule has been broken. You can also enter a default value for any of the numeric types. For a String the pane presents you with Minimum and Maximum length constraints. Again if the user attempts to save an entity with a string that violates either the .

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