abap webdynpro

Hi Sri,

<b>Lead Selection:</b>

A node's element collection can be accessed using a 1-based index value.

Exactly one element of the node collection can be marked as the element at

lead selection. The lead selection of a context node points to either a single

selected node element (value of the lead selection = number of the selected

node element) or, if no element is selected, it has the value of the constant

IF_WD_CONTEXT_NODE=>NO_SELECTION. The lead selection can be

set automatically by the Web Dynpro framework if the context node property

Initialize Lead Selection is set to true. In this case, the first element in a collection

will automatically be marked as the element at lead selection.The lead selection can also be set by program source code or it can be set by user actions related

to UI elements for example, mark line in table view element, which is bound

to the node).

• In the controller code, special methods can be used to access the lead

selection of a node, as well as its position.

• UI elements such as e input fields can be bound to the attributes of this

element.

<b>For Example :

if we want display two tables(Flights,Booking) in a view, Generally Display a all contents from Flights table and user select particular flight and display the booking details accroding to that selected flight into Second table in this view. from table one we selecting that flight using lead selection only.</b>

<b>If the lead selection is set, the following is true:</b>

<b>Singleton Property :</b>

The Boolean property Singleton critically affects the relationship between a dependent node and its parent node.

If the BOOKINGS node has its singleton property set to false (node BOOKINGS

at runtime will be a non-singleton), then for every element in the parent node

collection (FLIGHTS, in this case), there will be a distinct instance of the child

node BOOKINGS. node has its singleton property set to false (node BOOKINGS

at runtime will be a non-singleton), then for every element in the parent node

collection (FLIGHTS, in this case), there will be a distinct instance of the child

node BOOKINGS.

The most important thing to understand here is that each instance of the

BOOKINGS node is related to the respective element in the parent node collection.

<b>Ex:</b>

<b>Therefore, if there are n elements in the parent node, then there will be n distinct

instances of a non-singleton child node.</b>

<b>If the node BOOKINGS now has its Singleton property set to true (which is the

default), it does not matter how many elements are present in the parent node

collection (FLIGHTS, in this case). There will only ever be one instance of the

child node BOOKINGS, so the BOOKINGS collection will be a singleton at

runtime.</b>

<b>Supply Function :</b>

Supply functions are a mechanism to repopulate child nodes. A supply function

can be assigned to each context node of a controller. This supply function is

called by the runtime automatically when the data of an invalid context node is

accessed. Invalidation of a context node occurs under the following conditions:

&#149; The node collection is initial.

&#149; The lead selection in the parent node collection is changed.

&#149; The node collection is invalidated programmatically.

The supply function is especially useful in combination with singleton nodes. The

values of child node elements of the type Singleton depend on the element of the

parent node to which the lead selection is currently assigned. If the lead selection

is changed by the user, the supply function can access the new lead selection

element and recalculate the values of the child node elements accordingly.

The name of a supply function can be entered when defining or changing a context

node from its context menu. As a result, an instance method is generated with

a given signature:

&#149; A reference to the element at lead selection in the parent node allows access

to the attributes of this element.

&#149; A reference to the node the supply function is related to allows you to store

the dependent data in the child nodes collection.

if u have any clarification with this topic reply me,

Regards,

Vijay.

Message was edited by:

Vijay.V