{"id":28593,"date":"2013-06-27T14:29:51","date_gmt":"2013-06-27T08:59:51","guid":{"rendered":"http:\/\/vskills.in\/certification\/tutorial\/?p=28593"},"modified":"2024-04-12T14:16:12","modified_gmt":"2024-04-12T08:46:12","slug":"storage-3","status":"publish","type":"page","link":"https:\/\/www.vskills.in\/certification\/tutorial\/storage-3\/","title":{"rendered":"Storage"},"content":{"rendered":"

Certify and Increase Opportunity.<\/span>
\nBe <\/span>
\nGovt. Certified Blackberry Apps Developer
\n<\/span><\/a><\/p>\n

Data storage<\/h1>\n

Many apps that you create will need to manipulate data in some way. A contacts list app might need to load existing contacts from a data file and save new contacts in the file. A sports app might track team statistics in a data file and update these statistics after each game.<\/p>\n

The\u00a0Cascades\u00a0framework uses a modular approach to store, access, and display data in your apps. This approach makes it easy for you to store different types of data, organize and model the data in different ways, and display the data with different visual styles.<\/p>\n

The following diagram illustrates the different components that interact when you manipulate data in your app:<\/p>\n

\"cascades_data_access_elements_diagram_1\"<\/a><\/p>\n

External data<\/h3>\n

This component represents the raw data for your app. The data could be a list of contact entries, a set of financial records, or a group of game objects. You can access data that you package with your app, but you can also create new data dynamically as your app runs. The format of this data can vary depending on your needs, and\u00a0Cascades\u00a0provides classes that help you manage three common data formats: JSON, SQL, and XML.<\/p>\n

Data access<\/h3>\n

This component lets you access the external data and manipulate it in your app. You can load data files, create new files and save data in them, and handle any errors that might occur during these operations. Then, you can add the data to a data model to organize it before it’s displayed. You can use the<\/p>\n

JsonDataAccess<\/samp>,<\/p>\n

SqlDataAccess<\/samp>, and<\/p>\n

XmlDataAccess<\/samp>classes to load and save data in JSON, SQL, and XML format, respectively. You can also access SQL data asynchronously using an<\/p>\n

SqlConnection<\/samp>. Supporting classes, such as<\/p>\n

DataAccessError<\/samp>, give you more information about errors so you can handle them appropriately.<\/p>\n

Data source<\/h3>\n

This component is designed specifically as an easy-to-use adapter in QML between external data and UI components. You can use the<\/p>\n

DataSource<\/samp>class to declare the properties of the external data that you want to access. This data can be SQL, JSON, or XML data that’s stored locally, or it can be JSON or XML data feeds that are accessed remotely. You can also use the<\/p>\n

DataSource<\/samp>class to control when and where the data is loaded.<\/p>\n

Data model<\/h3>\n

This component lets you organize and sort your data, and then provide the data to a list view to display it. For example, you can use a<\/p>\n

GroupDataModel<\/samp>to sort a list of employees by last name or employee number. Then, you can associate this data model with a list view, and your data is organized and displayed in the way you specified.<\/p>\n