null component check in the view -- how does it work?

[allonrauer]

in the dvd store example, i notice that some of the view 'code' checks for null component values (e.g., <f:subview rendered="#{currentUser == null}">).

however, it looks like the SeamVariableResolver automatically creates a component when resolving a name:
public Object resolveVariable(FacesContext facesContext, String name) throws EvaluationException
{
name = name.replace('$', '.');

log.debug("resolving name: " + name);
Object component = Component.getInstance(name, true);

so how can the component value ever be null?

[holgerprause]

Well as far as i understand it works like this:

first, seam looks if a object for this variable exists, in all scopes, if none was found, seams looks if a component with such a name exists ->
(the code u posted) if yes , it will be created.


currentUser would only be never null when u write something like this:

@Name("currentUser")
public class User {
....
}

[gavin.king]

No, the reason is that some context variables do not have components bound to them.

In those cases, the app is responsible for explicitly setting the value of the context variable.