Groovy Goodness: Observable Map and List

Groovy provides the ObservableMap and ObservableList classes. These classes send out PropertyChangeEvent objects when we add, remove or change the contents of the map or list. For several actions we get different event types and we can use a PropertyChangeListener object to subscribe to these events. For example if we add an element we can subscribe to the property change event and get an PropertyAddedEvent.

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import java.beans.*   def event // Listener will assign event to global event variable. def listener = {     event = it } as PropertyChangeListener   /* ObservableList */ def list = ['Groovy', 'rocks', 'the world', true] as ObservableList list.addPropertyChangeListener(listener)   list << 'More text' assert event instanceof ObservableList.ElementAddedEvent assert 4 == event.index assert 'More text' == event.newValue   list.remove(3) assert event instanceof ObservableList.ElementRemovedEvent assert 3 == event.index   list[0] = 'Grails' assert event instanceof ObservableList.ElementUpdatedEvent assert 0 == event.index assert 'Groovy' == event.oldValue assert 'Grails' == event.newValue   list.addAll([42, 101]) assert event instanceof ObservableList.MultiElementAddedEvent assert [42, 101] == event.values   list.removeAll([true, 'More text', 42, 101]) assert event instanceof ObservableList.MultiElementRemovedEvent assert 3 == list.size()   list.clear() assert event instanceof ObservableList.ElementClearedEvent assert ['Grails', 'rocks', 'the world'] == event.values   event = null   // We can define a closure as a filter. The closure is // executed for each element and if it returns true, // the property change event is fired. def strict = new ObservableList({ it.size() > 2 }) strict.addPropertyChangeListener(listener) strict.addAll(['a', 'ab', 'abc', 'abcd']) assert ['abc', 'abcd'] == event.values   /* ObservableMap */ event = null   // Extra property change listener to assign to a specific // property instead of the whole map. def propEvent def propListener = { propEvent = it } as PropertyChangeListener   def map = [username: 'mrhaki', email: 'email@host.com', active: true] as ObservableMap map.addPropertyChangeListener(listener) map.addPropertyChangeListener("active", propListener)   map.location = "@work" assert event instanceof ObservableMap.PropertyAddedEvent assert 'location' == event.propertyName assert '@work' == event.newValue assert !propEvent   map.active = false assert event instanceof ObservableMap.PropertyUpdatedEvent assert propEvent instanceof ObservableMap.PropertyUpdatedEvent assert true == propEvent.oldValue assert false == propEvent.newValue assert 'active' == event.propertyName   map.remove('active') assert propEvent instanceof ObservableMap.PropertyRemovedEvent assert 3 == map.size()   map.putAll([car: true, phone: '555-1234']) assert event instanceof ObservableMap.MultiPropertyEvent assert event.events[0] instanceof ObservableMap.PropertyAddedEvent assert 'car' == event.events[0].propertyName assert true == event.events[0].newValue assert event.events[1] instanceof ObservableMap.PropertyAddedEvent assert 'phone' == event.events[1].propertyName assert '555-1234' == event.events[1].newValue   map.clear() assert event instanceof ObservableMap.PropertyClearedEvent assert [username: 'mrhaki', car: true, phone: '555-1234', location: '@work', email: 'email@host.com'] == event.values   def strictMap = new ObservableMap({ name, value -> name ==~ /^a.*/ }) strictMap.addPropertyChangeListener(listener) strictMap.putAll([a: 1, b: 2, c: 3]) assert 1 == event.events.size() assert 'a' == event.events[0].propertyName assert 1 == event.events[0].newValue