Extensions

• Extensions + Custom DAO builder function
• Custom conversion functions for transfer objects
• Custom data portal functions

Extension manager classes provide opportunities to change or extend the fumctioning of business objects. ExtensionManager is for asynchronous objects abd ExtensionManagerSync is for synchronous ones, respectively. Their constructors require two arguments:

• dataSource
  The name of the data source.
• modelPath
  The full path of the model.

Both arguments is used by the data access object builder function. Argument dataSource determines the path of the data access objects of the model, it can be any non-empty string. Argument modelPath is typically the __filename global object of node.js. The default builder of business-objects library creates the path of the data access object for the business object inserting the dataSource string into the modelPath as secondary extension:

// Path of the model definition file: /path/to/model.js
var extensions = new Extensions('dao', __filename);

// Path of data access object will be: /path/to/model.dao.js

For example argument dataSource can be the name of the database when the application uses multiple stores, or the name of the database type if the application supports multiple databases.

Extension manager classes have the following addtional properties:

// Custom DAO Builder function
extensions.daoBuilder = function() { };
// Custom conversion functions for transfer objects
extensions.toDto = function() { };
extensions.fromDto = function() { };
extensions.toCto = function() { };
extensions.fromCto = function() { };
// Custom data portal functions
extensions.dataCreate = function() { };
extensions.dataFetch = function() { };
extensions.dataInsert = function() { };
extensions.dataUpdate = function() { };
extensions.dataRemove = function() { };
extensions.dataExecute = function() { };

Custom DAO builder function

The data access object builder function can replaced globally in configuration. The extension manager provides a way to change it per model.

• daoBuilder( dataSource, modelPath, modelName )

The function composes the full path of the data access object using the arguments, reads the constructor of it and creates an instance of the type. If the data access object cannot be instantiated the function returns a DaoError object that describes the issue. The default data access object builder function works in a simplified way like that:

function daoBuilder( dataSource, modelPath, modelName ) {
  var daoPath = path.join(
    path.dirname(modelPath),
    path.basename(modelPath, path.extname(modelPath)) + '.' + dataSource + path.extname(modelPath)
  );
  var daoConstructor = require(daoPath);
  return new daoConstructor();
}

For more information see daoBuilder function.