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Build a Simple VCL Application for REST Data

How to build a simple VCL Application to view REST data in RAD Studio using the CData FireDAC Components for REST.

Embarcadero RAD Studio provides a development environment for Delphi and C++Builder applications. With the CData FireDAC Components for REST, you gain access to live REST data within RAD Studio, abstracting the data into tables, views, and stored procedures that can be used to both retrieve and update REST data. This article will walk through connecting to REST and creating a simple VCL application with the Form Designer.

Creating a VCL Application for REST Data

The following instructions show how to use the Form Designer to create a simple VCL Forms application that shows the basic FireDAC objects needed to connect to REST from any application.

The following example populates a TDBGrid control.

  1. Create a new VCL Forms Application.
  2. Drop a TFDPhysRESTDriverLink and TFDConnection object onto the form.
  3. Double-click the TFDConnection object. The FireDAC Connection Editor is displayed. Select "CData.REST" in the DriverId menu and configure the connection properties.

    See the Getting Started chapter in the data provider documentation to authenticate to your data source: The data provider models REST APIs as bidirectional database tables and XML/JSON files as read-only views (local files, files stored on popular cloud services, and FTP servers). The major authentication schemes are supported, including HTTP Basic, Digest, NTLM, OAuth, and FTP. See the Getting Started chapter in the data provider documentation for authentication guides.

    After setting the URI and providing any authentication values, set Format to "XML" or "JSON" and set DataModel to more closely match the data representation to the structure of your data.

    The DataModel property is the controlling property over how your data is represented into tables and toggles the following basic configurations.

    • Document (default): Model a top-level, document view of your REST data. The data provider returns nested elements as aggregates of data.
    • FlattenedDocuments: Implicitly join nested documents and their parents into a single table.
    • Relational: Return individual, related tables from hierarchical data. The tables contain a primary key and a foreign key that links to the parent document.

    See the Modeling REST Data chapter for more information on configuring the relational representation. You will also find the sample data used in the following examples. The data includes entries for people, the cars they own, and various maintenance services performed on those cars.

  4. Drop a TFDQuery object onto the form and set the properties below:

    • Connection - Set this property to the TFDConnection object, if this object is not already specified.
    • SQL - Click the button in the SQL property and enter a query.
    • Active - Set this property to true.
  5. Drop a TDataSource object onto the form and set the following property:

    • DataSet - In the menu for this property, select the name of the TFDQuery object.
  6. Drop a TDBGrid control onto the form and set the following property:

    • DataSource - Select the name of the TDataSource.
  7. Drop a TFDGUIxWaitCursor onto the form. This is required to avoid a run-time error.

You now have an executable application that displays the results of the SQL Query set in the TFDQuery object.

 
 
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