The <flow:interview> component is designed
to make it easy to develop complex Visualforce interactions. You can
access additional features in your flow by creating a custom controller. With custom
controllers, you can build a page with multiple components that can interact with each
other. Any flow within your organization can be individually referenced by its own Apex
type, and the variables in the flow can be accessed as member variables.
You
can set only variables that allow input access, and you can get only variables that
allow output access. For a variable that doesn’t allow input or output access, attempts to
get the variable are ignored, and compilation may fail for the Visualforce page, its <apex:page> component, or the Apex class.
For our next example, the flow with API name “ModemTroubleShooting” is
referenced as
Flow.Interview.ModemTroubleShooting. The markup illustrates how to display
a value of a flow variable in a different part of the
page:
If the flow is
from a managed package, the name attribute must be
in this format: namespace.flowuniquename.
The controller for the above markup looks like
this:
If you’re using a custom controller, you can also set the initial values of the
variables at the beginning of the flow in the constructor of the flow. Passing in
variables using the constructor is optional and isn’t necessary if you’re
using <apex:param> tags to set the value.
Here’s an example of a custom controller that sets the values of flow variables in
a
constructor.
You can use the getVariableValue method in the
Flow.Interview class to access the value of
a flow variable. The variable may be in the flow embedded in the Visualforce page or in
a separate flow that is called by a Subflow element. The returned variable value comes
from whichever flow the interview is currently running. If the specified variable
can’t be found in that flow, the method returns null. This method checks for the existence of the variable at run time
only, not at compile time.
This sample uses the
getVariableValue method to obtain breadcrumb
(navigation) information from a flow. If that flow contains subflow elements, and
each of the referenced flows also contains a
vaBreadCrumb
variable, you can provide users with breadcrumbs regardless of which flow the
interview is
running.
The following table shows the differences in the naming of supported data types between
the flow and Apex.
| Text |
String |
| Number |
Decimal |
| Currency |
Decimal |
| Date |
Date, DateTime |
| Boolean |
Boolean |
| Record, with a specified object |
The API name of the specified object, such as Account or
Case |
As it’s a good practice to write tests against your Apex code, the following is a
trivial example of writing a test class for
ModemTroubleShootingCustomSetVariables:
Setting the reRender Attribute
By using the reRender attribute, the <flow:interview /> component re-renders the
flow without refreshing the whole page:
If you don’t set the reRender attribute, when you click a button to navigate to a different
screen in a flow, the entire Visualforce page refreshes,
not just the <flow:interview>
component.
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