SD&D 101

OOP basics

1. Software Design 101  
2. string[] firstNames;! string[] lastNames;! ! string getName(string[] fNames, string[] lNames, int i)! {! "return fNames[i] + " " lNames[i];! }! Why? This is bad.
3. Lets pretend We have a School That has Students, Employees, Professors That are all People
4. Objects are “things” Encapsulate related activities e.g. Student, Professor, Person, School
5. Classes Represent Objects
6. class Student {! "string firstName;! "string lastName;! "int gradeLevel;! }! Student is an object
7. encapsulation Prevents pollution
8. class Student {! "public string getName() { return firstName+” “+lastName; } ! ! "private string firstName;! "private string lastName;! "private int gradeLevel;! }!
9. Interfaces are Contracts
10. interface IPerson {! "public string getName();! }! ! class Student : IPerson {! "public string getName() { return firstName+" “+lastName; } ! ! "private string firstName;! "private string lastName;! "private int gradeLevel;! }! All members must be implemented
11. Class Inheritance Reduces redundancy
12. class Person {! "public string getName() { return firstName+" "+lastName; } ! ! "private string firstName;! "private string lastName;! }! ! class Student : Person {! "private int gradeLevel;! }! ! class Professor : Person {! "private string department;! }!
13. Polymorphism Will confuse you quickly
14. class Person {! "public string getName() { return firstName+" "+lastName; } ! ! "private string firstName;! "private string lastName;! }! ! class Student : Person {! "private int gradeLevel;! }! ! class Employee : Person {! "private in employeeId;! }! ! class TA : Employee, Student {! "private string department;! }! An object can Inherit from multiple
15. Coupling vs cohesion
16. Coupling Loose Tight Student -> Professor Marriage
17. Cohesion Low High Walmart Highly related
18. Okay, But Why? Makes your code readable Avoids redundant code Keeps like things organized Avoids pollution
19. Questions? Complaints?
20. http://en.wikipedia.org/wiki/Object-oriented_programming! http://en.wikipedia.org/wiki/Class-based_programming! ! References