## More Patterns (cont.)

Pattern Name | Description | Example
--- | --- | ---
Mediator | An object encapsulates the interaction of other objects | All components in a dialog box notify a mediator of state changes. The mediator updates affected components
Memento | An object yields an opaque snapshot of a part of its state, and can later return its state from that snapshot | An undo mechanism requests a memento from an object before mutating it. If the operation is undone, the memento is used to roll the object back to its old state
Observer | An object wants to be notified when another object generates an event | User interface components generate events, such as button clicks and text changes. A dialog box observes the events and repaints its contents

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