#  Copyright (c) 2007, Enthought, Inc.
#  License: BSD Style.

# list_notifier.py -- Example of zero-parameter handlers for an object
#                     containing a list

#--[Imports]--------------------------------------------------------------------
from traits.api import HasTraits, List

#--[Code]-----------------------------------------------------------------------

class Employee: pass

class Department( HasTraits ):
    employees = List(Employee)

#--[Example*]-------------------------------------------------------------------

def a_handler(): print "A handler"
def b_handler(): print "B handler"
def c_handler(): print "C handler"

fred = Employee()
mary = Employee()
donna = Employee()

dept = Department(employees=[fred, mary])

# "Old style" name syntax
# a_handler is called only if the list is replaced:
dept.on_trait_change( a_handler, 'employees' )
# b_handler is called if the membership of the list changes:
dept.on_trait_change( b_handler, 'employees_items')

# "New style" name syntax
# c_handler is called if 'employees' or its membership change:
dept.on_trait_change( c_handler, '[employees]' )

print "Changing list items"
dept.employees[1] = donna     # Calls B and C
print "Replacing list"
dept.employees = [donna]      # Calls A and C