We were asked to go to Poundland with £10 to spend on getting items that would help us teach a Computing lesson. My colleague and I chose to teach the fundementals of OOP and objects usin a selection of toys that we bought – eg some rubber balls, plastic cars, dinosaurs etc.
Here is the outline of teh mini lessonw e gave to our peers:
OOP – Classes, Sub Classes, Inheritance, Properties & Methods
STARTER Get toys out on the table
“What are all these items?” Answer – hopefully “Toys”
These items are all part of the Class of “Toys”
They have similar properties – you can play with them – what else??
What groups can you see here? Get toys and group them by type – eg cars, animals, soft toys
These can be called sub classes which inherit characteristics from the parent class
Pick up two cars.
These are both in the class “Car”
Eg Yellow car and blue car
“These are instances of Car – they are objects or the class Car”
We could name them “YellowCar” and “BlueCar” – or Car1 and Car2
Each car has properties – pieces of information about each car – eg
- Number of Doors etc
Can you think of any others?
Properties are essentially static – you can’t easily change them – just read the value
Can you think of some properties of any of the other groups of classes?
E.g. Dinosaurs –
- Number of legs
- Has it got spikes?
Challenge can you think of a property for the Toys superclass? (eg suitable age, material made of, needs batteries?)
Properties of the parent class are automatically “inherited” by the sub classes
So if the Toy parent class has a property of “suitable age” then the Cars classes will inherit it, so it will also have that property.
Methods are the actions that an object can perform
Eg A car can drive or stop
A Dinosaur can attack
A ball can bounce or be thrown