Co517 Object Oriented Programming

Front 1

data hiding

Back 1

making class members unavailable to programs

do this to get the extra variables out of the way

normally if a class is programmed correctly, all interaction should be through methods rather than fields. this helps when changing the way the class works without without changing the actions

Front 2

scope resolution operator

Back 2

the operator "::" in "ret_type class::function()"

tells compiler that 'function' of return type 'ret_type' is a method in 'class'

this trick allows programmer to define a method outside the class definition, conditional on the method having been declared within the class definition

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constructor

Back 3

function that initialises a class instance and allocates memory for it

its name is same as the class whose objects it constructs

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destructor

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function that deletes memory for a class instance when it goes out of scope

its name is same as constructor, with '~' in front

DON'T FORGET TO DEALLOCATE ALL MEMORY WITH THIS GUY

Front 5

containership

Back 5

when a class contains other class(es)

advantage: consider class Car, containing classes Wheel, Gear, Engine.
consider a Car object. If a gear were to be changed, you would simply have to assign a corresponding new Gear object to the car. you wouldn't need to create a whole new Car object.

Front 6

inheritance/derivation

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when a class contains all the fields and methods of another class

not the same as containing another class!

eg a batmobile derives from a car hence inherits its fields and methods; a car contains a wheel and so has a Wheel object as a field

syntax: "class Batmobile : public Car {...}"

Front 7

scope resolution operator within a derived class

Back 7

this is when it gets really handy: if within Batmobile class you want to make use of a Car method called 'function', you would type "Car::function()"

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UML

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unified modelling language

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attribute

Back 9

==field, data field, member

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operations

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==method, member function, member routine

if an operation involves multiple objects, assign it to the one who performs the action

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association: define, give UML representation

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denotes a relationship between 2 classes

can be multiple associations between classes, eg Person has the "colleague" association to itself, and also "friend"

in UML, represented as an edge between two class nodes

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association::role
define, give UML representation

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in an association between 3 classes, each class plays a role.

in UML, represented by endpoint of an association edge; description of role is labelled below intersection of edge and node

Front 13

association::multiplicity
define, give examples, give IML representation

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when an association involves a class with multiple instances of the associated class

eg Child involves 2 instances of Parent
eg Company involves 0...* employees

in UML, labelled above intersection of edge and node, above role label

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association::aggregation
define, give examples, give UML representation

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association in which a class is contained in another

eg Wheel composes (among others) Car

in UML, represented as diamond-tipped directed edge

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aggregation::element
aggregation::aggregate

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if A is contained in B, B is the element and A is the aggregate in the aggregation

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aggregation::shared aggregation: define using 'element' and 'aggregate', give example

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aggregation in which element can belong to multiple aggregates - i.e. element is shared between multiple aggregates

eg a department contains students, but a student can belong to multiple departments, so there is shared aggregation from Student to Department

Front 17

aggregation::composition

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aggregation in which element belongs to at most one aggregate

so composition = ¬shared_aggregation