Object Oriented Concepts

Front 1

What is the goal of Software Architecture

Back 1

1. Partition the problem
2. Create interfaces
3. Manage overall structure and flow
4. State how system interfaces with its environment
5. Recommend tools and techniques to build system

Front 2

Why Software Architecture is important

Back 2

1. Controls complexity
2. Enforces best practices
3. Gives consistency
4. Increases predictability
5. Enables re-use

Front 3

What is an Object

Back 3

It can be considered a "thing" that can perform a set of related activities.
In OOP terms it is an "instance" of a class.

Front 4

What is a Class

Back 4

a blueprint/plan/template for an object

Front 5

Name 5 principles to follow in designing a class

Back 5

S.O.L.I.D.
1. SRP - Single Responsibility
2. OCP- Open Closed
3. LSP - Liskov Substitution
4. ISP - Interface Segregation
5. DIP - Dependency Inversion

Front 6

What is the "Single Responsibility Principle" (SRP)

Back 6

A class should have one, and only one, reason (or responsibility) to exist. That responsibility should be entirely encapsulated by the class.

Front 7

What is the Open Closed Principle (OCP)

Back 7

You should be able to extend a class behavior without modifying it.

Front 8

What is the Liskov Substitution Principle (LSP)

Back 8

If a statement is true for a base class, then you should be able to use (in the statement) an instance of a derived class. The statement should still be valid.

I.E.: if the class "animal" has a certain capability ... then so should the class "dog", if "dog" is derived from "animal".

Front 9

What is the Interface Segregation Principle (ISP)

Back 9

Make fine grained interfaces that are client specific.

Front 10

What is the Dependency Inversion Principle (DIP)

Back 10

Depend on generalities (abstractions), not on concrete implementations.

Front 11

What concepts group OOP system-design techniques

Back 11

"A PIE" (mnemonics)
1. Abstraction
2. Polymorphism
3. Inheritance
4. Encapsulation

Front 12

What is Encapsulation

Back 12

The inclusion, within an object, of all the resources (attributes, data & methods) it needs to function

Front 13

What basic (relationship) techniques can be used to "link" classes with each other

Back 13

1. Association
2. Aggregation
3. Composition

(note: each forms a 'subset' of the one above)

Front 14

What is "Association"

Back 14

Most general relationship between classes, as: companies "use" security guards (but don't HAVE to).

Front 15

What is "Aggregation"

Back 15

A directional type of "Association" between classes that indicates inclusion and is usually stated using forms of the verb "to have", as in: companies have (sometimes) security-guards.

Front 16

What is "Composition"

Back 16

An "Aggregation" of one class within another which indicates that the lifetime of the two classes is linked: like University and Faculties. It's usually stated by the phrase "composed of", as "a University is composed of faculties. If the university closes ... the (isolated) existence of its faculties does not make sense.

Front 17

What is abstraction

Back 17

A means to reduce complexity by hiding irrelevant details of an object & emphasizing its reason for existence, its qualities and its properties. It emphasizes the "what", rather than the "how".

Front 18

What is generalization

Back 18

A means to reduce complexity by replacing multiple entities that perform similar functions with a single one.

I.E.: the overloading of the "+" operator to work on numbers (addition) and strings (concatenation)

Front 19

How do programming languages provide means to use generalization

Back 19

1. variables
2. parametrization
3. generics
4. polymorphism

Front 20

What is an Abstract class

Back 20

1. A template, or "super-class", for other classes.
2. Contains at least one or more "stubs", or abstract methods/properties.
3. Can NOT be instantiated
4. Can be "extended" by another class by overriding ALL its abstract methods/properties.
5. Can have a default constructor, but it must be marked "protected", so it's "auto-called" while instantiating sub-class.

Front 21

What is an Interface

Back 21

1. Defines a "contract", not an implementation.
2. Can have properties.
3. Method stubs and properties are, implicitly, public and abstract.
4. Can't be instantiated.

Front 22

Describe how to mark a class that implements an interface, but not all of its methods.

Back 22

1. Subclass must be marked abstract
2. Non-implemented methods/properties must be marked both: public & abstract

Front 23

What method modifier (public, private, ... etc) are allowed on interface methods.

Back 23

Only the "new" modifier is allowed, indicating that it hides a method of the same name on an inherited interface.

Front 24

If a class, interface or struct is not marked with an access modifier, what access level does it get by default: public, private, protected, internal

Back 24

internal

Front 25

What modifiers are valid in C# interface methods (public, private, protected, internal, new, static

Back 25

"new" is the ONLY valid modifier in an interface method. The method is, by default, also "public" & "abstract", but it should not be marked as such.

Front 26

Assuming the following class/interface are at a global scope (not nested within another class or interface): are these snips of code OK?:

protected class MyClass{ ... }
protected interface MyInterface{ ... }

Back 26

No, the ONLY access modifiers valid on a (global) class/interface are "public" and "internal"

Front 27

Can a C# class, or interface, be nested within another interface

Back 27

No, classes and interfaces can NOT be nested within another interface.

Front 28

If a method is declared "virtual" in a base class, what is the difference between "overriding" it, or marking it "new", in a derived class.

Back 28

If an object, Obj, is defined as an instance of a derived class, then:

1. If a method is overridden in the derived class Obj will use the overridden method whether or not Obj is declared as base or as derived.

2. If a method is declared "new" in the derived class, Obj will use the base method if it is declared as base ... and the "new" method if it is declared as derived.

Front 29

What is (object) polymorphism

Back 29

Means: "many-shaped", and means an object can behave as an instance of multiple classes.

1. at run-time (as a parameter, etc) the object may be treated as being an instance of:
i) the class that was used to instantiate it.
ii) any of its base classes.

2. base class "virtual" methods can be "overridden" by the derived class and thus be called on the object EVEN when the object is declared an instance of the base class.

Front 30

What is method overloading

Back 30

Is a form of method polymorphism: the ability to define several methods all with the same name.

Front 31

What is operator overloading

Back 31

A type of method polymorphism that causes operators (+, -, ==, *) to behave differently depending on the type of its arguments.

Front 32

What is method overriding

Back 32

A "virtual" method, if "overridden" in a subclass, causes the new method to be invoked on the object EVEN when the derived object is declared/used as if it were an instance of its base class.

If you want the original method to still be available when the derived object is declared as base, use the "new" keyword instead of overriding.

Front 33

What is a "use case"

Back 33

It is the description of what an "actor" (not necessarily a person) perceives when using a function of a software system.