Difference between CallBack and Listener and Observer as Design Pattern
- CallBack
Brief
After the specific processing ends, registered callback object is called.
E.g.
In advance, pass phone number to callback object.
After active processing like ‘Taking photo’ ends, notify callback object and execute methods.
- Listener
Brief
When the specific events occurred, registered listener objects are called.
E.g.
In advance, listers are registered by an object which controls passive processing.
After passive processing like ‘Touch screen’ is executed, notify registered listeners and execute specific methods.
- Observer
Brief
When the specific states were changed, registered observer objects are called. Mostly same as lister pattern.
E.g.
After battery charge remaining is less, notify registered observers and execute specific methods..
The difference between callback and listener is that events when they are called are active or passive.
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