In most cases, you use the Database, XPath, or Association data sources to fill a data widget. For example, if the properties of a data grid require an object of an entity selected in the data grid, the data grid gets its objects from a database query. Another example is that a nested template grid can retrieve its objects over an association. However, sometimes the target objects need to adhere to very specific criteria, or different objects are shown under different circumstances that cannot be handled by an XPath. In these situations a Microflow data source may be required.
When a data widget with a microflow data source is displayed in the browser or refreshed, it runs the designated microflow and displays the return value. The manner in which the objects are acquired in the microflow is entirely up to you, which allows for unlimited control over what objects to return.
A microflow data source ignores all context. It performs the actions described in the microflow, nothing else. For example, nested data containers with a microflow data source will not automatically create or invoke associations to the encasing data widget.
When Microflow is selected as the data source, this is regarded as “indirect usage.” This means that you cannot also select an Entity (path) as you can with the Database, XPath, or Association data source types.
2 Microflow Data Source Example
In this scenario, you have a data grid that needs to display a list of potential orders based on the order type:
If the OrderType of the Order entity is set to Cars, then the data grid should display all the Products for which the Boolean Motorized is set to true. If the OrderType is Bicycles, only objects for which Motorized is set to false need be shown. Finally, if OrderType is empty, the data grid should remain empty.
Because of the mismatch in attribute types, this cannot be constrained by XPath, so a microflow data source is required.
The microflow for this scenario should look like this:
This microflow does the following:
- It passes the Order of the enclosing data view as a parameter.
- It then splits on the OrderType attribute and retrieves a different set of products for each enumeration value.
- It returns a list of products, and each end event is configured to return a list. Note that the empty path also requires a value, wherein empty is also a value.
This designates the microflow to be used to populate the data widget. This microflow will be run whenever the data widget is loaded into the browser or refreshed. The microflow must have a return value of either an object or a list of objects, depending on the data widget being used.
3.2 Microflow Settings
Microflow settings opens a dialog box enabling you to specify what parameters will be passed to the microflow.
This duplicates the Microflow specified above.
3.2.2 Microflow Arguments
Microflow arguments are automatically configured based on the parameters of the selected microflow and the available arguments. In general arguments are taken from any enclosing data widget. If the data widget enclosing the widget calling a microflow is inside another (nested) data widget, then objects from that data widget and any others in which it is nested can also be passed.