Classes

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Classes
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What is a class?

• Data and the functions (methods) that operate on
  that data collectively called members
• Example bank account class
• Provide structure for organizing programs
• Almost like an advanced struct

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Syntax

• class classname
• private
• public
• private only accessible within the class
• public accessible from anywhere (like with a
  struct)

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Member Functions

• Typically, data (variables) declared private
• Functions operate on data
• accessor functions read data, provide access to
  data but do not change it
• update functions change data
• examples from bank account, zoo???
• constructor builds a new object

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Object-Oriented Design

• Method for designing computer programs
• Consider objects interacting in the program
• Example a zoo, coffee machine, grade book
• The behavior of each kind of object is defined in
  a class

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Writing Classes

• Typically, two files header and source
• Header declares member variables, provides
  function prototypes and bodies of short functions
• Source provides code for rest of functions
• When specifying function bodies outside of class
  definition must be used
• void BankAccountwithdraw(double amount)

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Creating and Using Objects

• BankAccount b(Sami Rollins)
• //Type Name(constructor parameters)
• //how would you withdraw funds?

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Creating and Using Objects

• BankAccount b(Sami Rollins)
• Type Name(constructor parameters)
• //how would you withdraw funds?
• b.withdraw(300)
• object_name.method_name(param list)

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Constructor

• BankAccountBankAccount(double init_balance)
• class_name(parameter list)
• Special-case function called when a new object is
  created
• Used to initialize member variables
• Examples?

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Alternative Initialization

• BankAccountBankAccount(double init_balance)
• balance init_balance
• BankAccountBankAccount(double init_balance)
  balance(init_balance)

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Destructor

• BankAccountBankAccount()
• class_name
• Used if class allocates memory dynamically (uses
  new)
• Delete all dynamically declared objects

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friend

• Allow a class to access the private members of
  another class
• Operator overloading
• Closely related classes

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STL and Templates

• STL Standard Template Library
• collection of classes useful for many programs
• Templates
• a class which can hold objects of any kind
• vectorltintgt scores(100)
• vectorltBankAccountsgt bank_records(500)
• Vector resizable array