C++ Programming: Classes and Data Abstraction (Chapter 10) PDF

Chapter 10 Classes and Data Abstraction C++ Programming: From Problem Analysis to Program Design, Eighth Edition 1  Objectives (1 of 2) In this chapter, you will: – Learn about classes – Learn about pri...

Chapter 10 Classes and Data Abstraction C++ Programming: From Problem Analysis to Program Design, Eighth Edition 1  Objectives (1 of 2) In this chapter, you will: – Learn about classes – Learn about private, protected, and public members of a class – Explore how classes are implemented – Become aware of accessor and mutator functions – Examine constructors and destructors © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 2 or otherwise on a password-protected website for classroom  Objectives (2 of 2) Learn about the abstract data type (ADT) Explore how classes are used to implement ADTs Become aware of the differences between a struct and a class Learn about information hiding Explore how information hiding is implemented in C++ Become aware of inline functions of a class Learn about the static members of a class © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 3 or otherwise on a password-protected website for classroom  Classes (1 of 4) Object-oriented design (OOD): a problem solving methodology Object: combines data and the operations on that data in a single unit Class: a collection of a fixed number of components Member: a component of a class © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 4 or otherwise on a password-protected website for classroom  Classes (2 of 4) The general syntax for defining a class: A class member can be a variable or a function If a member of a class is a variable It is declared like any other variable You cannot initialize a variable when you declare it © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 5 or otherwise on a password-protected website for classroom  Classes (3 of 4) If a member of a class is a function A function prototype declares that member Function members can (directly) access any member of the class A class definition defines only a data type No memory is allocated Remember the semicolon (;) after the closing brace © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 6 or otherwise on a password-protected website for classroom  Classes (4 of 4) Three categories of class members: private (default) - Member cannot be accessed outside the class public - Member is accessible outside the class protected © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 7 or otherwise on a password-protected website for classroom  Unified Modeling Language Class Diagrams (1 of 2) Unified Modeling Language (UML) notation: used to graphically describe a class and its members +: member is public -: member is private #: member is protected © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 8 or otherwise on a password-protected website for classroom Unified Modeling Language Class Diagrams (2 of 2) FIGURE 10-1 UML class diagram of the class clockType © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 9 or otherwise on a password-protected website for classroom  Variable (Object) Declaration Once defined, you can declare variables of that class type clockType myClock; clockType yourClock; A class variable is called a class object or class instance FIGURE 10-2 Objects myClock and yourClock © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 10 or otherwise on a password-protected website for classroom  Accessing Class Members Once an object is declared, it can access the members of the class The general syntax for an object to access a member of a class: If an object is declared in the definition of a member function of the class, it can access the public and private members The dot (.) is the member access operator 11 © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom  Built-in Operations on Classes Most of C++’s built-in operations do not apply to classes Arithmetic operators cannot be used on class objects unless the operators are overloaded Relational operators cannot be used to compare two class objects for equality Built-in operations that are valid for class objects: Member access (.) Assignment (=) 12 © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom Assignment Operator and Classes FIGURE 10-3 myClock and yourClock before and after executing the statement myClock = yourClock; © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 13 or otherwise on a password-protected website for classroom  Class Scope (1 of 2) A class object can be automatic or static Automatic: created when the declaration is reached and destroyed when the surrounding block is exited Static: created when the declaration is reached and destroyed when the program terminates A member of a class has the same scope as a member of a struct © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 14 or otherwise on a password-protected website for classroom  Class Scope (2 of 2) A member of the class is local to the class You access a class member outside the class by using the class object name and the member access operator (.) © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 15 or otherwise on a password-protected website for classroom  Functions and Classes Objects can be passed as parameters to functions and returned as function values As parameters to functions: Class objects can be passed by value or by reference If an object is passed by value: Contents of data members of the actual parameter are copied into the corresponding data members of the formal parameter © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 16 or otherwise on a password-protected website for classroom  Reference Parameters and Class Objects (Variables) (1 of 2) Passing by value might require a large amount of storage space and a considerable amount of computer time to copy the value of the actual parameter into the formal parameter If a variable is passed by reference: The formal parameter receives only the address of the actual parameter © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 17 or otherwise on a password-protected website for classroom  Reference Parameters and Class Objects (Variables) (2 of 2) Pass by reference is an efficient way to pass a variable as a parameter Problem: when passing by reference, the actual parameter changes when the formal parameter changes Solution: use const in the formal parameter declaration © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 18 or otherwise on a password-protected website for classroom  Implementation of Member Functions (1 of 4) Must write the code for functions defined as function prototypes Prototypes are left in the class to keep the class smaller and to hide the implementation To access identifiers local to the class, use the scope resolution operator, (::) © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 19 or otherwise on a password-protected website for classroom Implementation of Member Functions (2 of 4) FIGURE 10-4 myClock before and after executing the statement myClock.setTime(3, 48, 52); © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 20 or otherwise on a password-protected website for classroom Implementation of Member Functions (3 of 4) FIGURE 10-5 Objects myClock and yourClock FIGURE 10-6 Object myClock and parameter otherClock © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 21 or otherwise on a password-protected website for classroom  Implementation of Member Functions (4 of 4) Once a class is properly defined and implemented, it can be used in a program A program that uses/manipulates objects of a class is called a client of that class When you declare objects of the class clockType, each object has its own copy of the member variables (hr, min, and sec) These variables are called instance variables of the class Every object has its own copy of the data © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 22 or otherwise on a password-protected website for classroom  Accessor and Mutator Functions Accessor function: member function that only accesses the value(s) of member variable(s) Mutator function: member function that modifies the value(s) of member variable(s) Constant member function Member function that cannot modify member variables of that class Member function heading with const at the end 23 © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom  Order of public and private Members of a Class C++ has no fixed order in which to declare public and private members By default, all members of a class are private Use the member access specifier public to make a member available for public access © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 24 or otherwise on a password-protected website for classroom  Constructors (1 of 2) Use constructors to guarantee that member variables of a class are initialized Two types of constructors With parameters Without parameters (default constructor) Other properties of constructors Name of a constructor is the same as the name of the class A constructor has no type © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 25 or otherwise on a password-protected website for classroom  Constructors (2 of 2) A class can have more than one constructor Each must have a different formal parameter list Constructors execute automatically when a class object enters its scope They cannot be called like other functions Which constructor executes depends on the types of values passed to the class object when the class object is declared © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 26 or otherwise on a password-protected website for classroom  Invoking a Constructor A constructor is automatically executed when a class variable is declared Because a class may have more than one constructor, you can invoke a specific constructor © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 27 or otherwise on a password-protected website for classroom  Invoking the Default Constructor Syntax to invoke the default constructor is: The statement: clockType yourClock; declares yourClock to be an object of type clockType and the default constructor executes © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 28 or otherwise on a password-protected website for classroom  Invoking a Constructor with Parameters The syntax to invoke a constructor with a parameter is: Number and type of arguments should match the formal parameters (in the order given) of one of the constructors Otherwise, C++ uses type conversion and looks for the best match Any ambiguity causes a compile-time error © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 29 or otherwise on a password-protected website for classroom  Constructors and Default Parameters A constructor can have default parameters Rules for declaring formal parameters are the same as for declaring default formal parameters in a function Actual parameters are passed according to the same rules for functions A default constructor is a constructor with no parameters or with all default parameters © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 30 or otherwise on a password-protected website for classroom  Classes and Constructors: A Precaution If a class has no constructor(s), C++ provides the default constructor However, the object declared is still uninitialized If a class includes constructor(s) with parameter(s), but not the default constructor C++ does not provide the default constructor Appropriate arguments must be included when the object is declared © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 31 or otherwise on a password-protected website for classroom  In-line Initialization of Data Members and the Default Constructor C++11 standard allows member initialization in class declarations Called in-line initialization of the data members When an object is declared without parameters, then the object is initialized with the in-line initialized values If declared with parameters, then the default values are overridden by the constructor with the parameters © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 32 or otherwise on a password-protected website for classroom  Arrays of Class Objects (Variables) and Constructors If you declare an array of class objects, the class should have the default constructor The default constructor is typically used to initialize each (array) class object © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 33 or otherwise on a password-protected website for classroom  Destructors Destructors are functions without any type A class can have only one destructor The destructor has no parameters The name of a destructor is the tilde character (~) followed by the class name Example: ~clockType(); The destructor automatically executes when the class object goes out of scope 34 © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom  Data Abstract, Classes, and Abstract Data Types Abstraction Separating design details from usage Separating the logical properties from the implementation details Abstraction also applicable to data Abstract data type (ADT): a data type that separates the logical properties from the implementation details Three things associated with an ADT Type name: the name of the ADT Domain: the set of values belonging to the ADT Set of operations on the data © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 35 or otherwise on a password-protected website for classroom  A struct versus a class (1 of 2) By default, members of a struct are public private specifier can be used in a struct to make a member private By default, the members of a class are private classes and structs have the same capabilities © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 36 or otherwise on a password-protected website for classroom  A struct versus a class (2 of 2) In C++, the definition of a struct was expanded to include member functions, constructors, and destructors If all member variables of a class are public and there are no member functions: Use a struct © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 37 or otherwise on a password-protected website for classroom  Information Hiding (1 of 3) Information hiding refers to hiding the details of the operations on the data The header file (or interface file) contains the specification details The header file has an extension h The implementation file contains the definitions of the functions to implement the operations of an object This file has an extension cpp In the header file, include function prototypes and comments that briefly describe the functions Specify preconditions and/or postconditions 38 © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom  Information Hiding (2 of 3) Implementation file must include the header file via the include statement In the include statement: User-defined header files are enclosed in double quotes System-provided header files are enclosed between angular brackets © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 39 or otherwise on a password-protected website for classroom  Information Hiding (3 of 3) Precondition: a statement specifying the condition(s) that must be true before the function is called Postcondition: a statement specifying what is true after the function call is completed © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 40 or otherwise on a password-protected website for classroom  Executable Code To use an object in a program The program must be able to access the implementation details of the object IDEs Visual C++ Express (2013 or 2016) and Visual Studio 2015, and C++ Builder put the editor, compiler, and linker into a package One command (build, rebuild, or make) compiles program and links it with the other necessary files These systems also manage multiple file programs in the form of a project © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 41 or otherwise on a password-protected website for classroom  More Examples of Classes Various examples of classes and how to use them in a program are presented Refer to Example 10-8 through Example 10-11 © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 42 or otherwise on a password-protected website for classroom  Inline Functions An inline function definition is a member function definition given completely in the definition of the class Saves the overhead of a function invocation Very short definitions should be defined as inline functions © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 43 or otherwise on a password-protected website for classroom  static Members of a Class (1 of 2) Use the keyword static to declare a function or variable of a class as static A public static function or member of a class can be accessed using the class name and the scope resolution operator static member variables of a class exist even if no object of that class type exists © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 44 or otherwise on a password-protected website for classroom  static Members of a Class (2 of 2) Multiple objects of a class each have their own copy of non- static member variables All objects of a class share any static member of the class © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 45 or otherwise on a password-protected website for classroom  Quick Review (1 of 3) A class is a collection of a fixed number of components Components of a class are called the members of the class Accessed by name Classified into one of three categories: private, protected, and public In C++, class variables are called class objects or class instances or, simply, objects © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service 46 or otherwise on a password-protected website for classroom  Quick Review (2 of 3) The only built-in operations on classes are assignment and member selection Constructors guarantee that data members are initialized when an object is declared A default constructor has no parameters The destructor automatically executes when a class object goes out of scope A class can have only one destructor The destructor has no parameters 47 © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom  Quick Review (3 of 3) An abstract data type (ADT) is a data type that separates the logical properties from the implementation details A public static member, function or data, of a class can be accessed using the class name and the scope resolution operator, :: static member variables of a class exist even when no object of the class type exists Instance variables are non-static data members 48 © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom