Flex Interview Questions

Difference between item renderer and item editors are as follows;

• Both are used for the purpose of editing, but item renderer is used for displaying visual elements.
• Item editor is used for editing purpose. Item editor can pass data back from the particular control to save it as a new value for an item being edited. We can also use item renderer as editor by using Boolean property renders editor.
• Item renderer is used to format and display the contents in components whereas item editor allows us to edit the displayed content

This method is used as it protects the events that represent changes to the underlying data from being broadcast by the view. It also stops the whole collection from being updated. This method is found to be very effective where multiple items in a collection are being edited at once. By disabling the auto update the changes are received as a batch instead of multiple events.

A cursor is an instrument used for position indicator, it points to any particular item. View cursor is used in order to traverse items in a collection data view and modify the data that is already stored in a collection. The move Next and move Previous to move the cursor forward or backward.

The filter function is used to limit the data view in the collection to any particular subset of source data. The function must be able to adopt a single object parameter that corresponds to a collection item and it is just to return a Boolean value specifying whether to include the item in the view or not.

The metadata is the tag used for providing information to the Flex compiler regarding the usage of the component.

Exclude (or Exclude Class) tag helps to control the set of choices, available in Flex Builder. But it never excludes the classes from linking. There is an MXML option that depends on how the application is been compiled. Generally, the classes that are included are those that are referenced from the root application or classes, either directly or via some other class that is referenced directly or not from the root application or classes.

View states give one way to change the look and feel of a component in response to user action. And a navigation controller can also be used e.g. Tab navigator etc. It depends on the user to select the navigation as per their requirements.
View stack is a component used to display different data, at once. View states are related views of a single set of data.
View stack components cannot be shared easily between the different views, they had to be created each time view is changed.

One can clearly spot lots of syntactic and non-syntactic differences between the two, but the major difference is: In Flex 4 the architecture of components have been changed. These components called Spark the older ones in Flex 3 are called Halo have separated the individual role as a developer and a designer. Spark components have one main core component class that contains the main logical part.

Cairngorm architecture can be explained as the process of implementation of several design patterns in order to form a lightweight architectural framework. Cairngorm follows the process of separating the view and business logic. This process is known as the Model-View-Controller pattern or (MVC).

The types of Cairngorm architecture are as follows:

• Model Locator: This Stores all the application’s Value along with shared variables that too at one place.
• View: This allows one or more Flex components bundled just like a named unit, bound to data in the Model Locator.
• Front Controller: This receives Cairngorm event details and then works ahead to map them to the cairngorm commands as and when required.
• Command: This handles business logic, calls cairngorm Delegates or Commands, and other updates.
• Delegate: This is created by a command, and regulates the remote procedure calls and gives the results back to that old command.
• Service: This defines the remote procedure calls to connect to remote data stores.

Difference between array and array collection is as follows:

• Array Collection is a wrapper class based on Array.
• Array Collection includes sorting, filtering features apart from Array.
• Array Collection automatically refreshes/updates the view whenever the change happens in Array Collection.

In order to cancel the default behavior of the event, few classified ways of the event class can be used in event listener functions in order to affect the behavior. In this few events are associated with default behavior. Therefore in cases, the same event listener can cancel the behavior by using the prevent Default method. Prevent Default method will work only if the Cancellable property is true else it will not.