- •Contents
- •Introduction
- •Who This Book Is For
- •What This Book Covers
- •How This Book Is Structured
- •What You Need to Use This Book
- •Conventions
- •Source Code
- •Errata
- •p2p.wrox.com
- •The Basics of C++
- •The Obligatory Hello, World
- •Namespaces
- •Variables
- •Operators
- •Types
- •Conditionals
- •Loops
- •Arrays
- •Functions
- •Those Are the Basics
- •Diving Deeper into C++
- •Pointers and Dynamic Memory
- •Strings in C++
- •References
- •Exceptions
- •The Many Uses of const
- •C++ as an Object-Oriented Language
- •Declaring a Class
- •Your First Useful C++ Program
- •An Employee Records System
- •The Employee Class
- •The Database Class
- •The User Interface
- •Evaluating the Program
- •What Is Programming Design?
- •The Importance of Programming Design
- •Two Rules for C++ Design
- •Abstraction
- •Reuse
- •Designing a Chess Program
- •Requirements
- •Design Steps
- •An Object-Oriented View of the World
- •Am I Thinking Procedurally?
- •The Object-Oriented Philosophy
- •Living in a World of Objects
- •Object Relationships
- •Abstraction
- •Reusing Code
- •A Note on Terminology
- •Deciding Whether or Not to Reuse Code
- •Strategies for Reusing Code
- •Bundling Third-Party Applications
- •Open-Source Libraries
- •The C++ Standard Library
- •Designing with Patterns and Techniques
- •Design Techniques
- •Design Patterns
- •The Reuse Philosophy
- •How to Design Reusable Code
- •Use Abstraction
- •Structure Your Code for Optimal Reuse
- •Design Usable Interfaces
- •Reconciling Generality and Ease of Use
- •The Need for Process
- •Software Life-Cycle Models
- •The Stagewise and Waterfall Models
- •The Spiral Method
- •The Rational Unified Process
- •Software-Engineering Methodologies
- •Extreme Programming (XP)
- •Software Triage
- •Be Open to New Ideas
- •Bring New Ideas to the Table
- •Thinking Ahead
- •Keeping It Clear
- •Elements of Good Style
- •Documenting Your Code
- •Reasons to Write Comments
- •Commenting Styles
- •Comments in This Book
- •Decomposition
- •Decomposition through Refactoring
- •Decomposition by Design
- •Decomposition in This Book
- •Naming
- •Choosing a Good Name
- •Naming Conventions
- •Using Language Features with Style
- •Use Constants
- •Take Advantage of const Variables
- •Use References Instead of Pointers
- •Use Custom Exceptions
- •Formatting
- •The Curly Brace Alignment Debate
- •Coming to Blows over Spaces and Parentheses
- •Spaces and Tabs
- •Stylistic Challenges
- •Introducing the Spreadsheet Example
- •Writing Classes
- •Class Definitions
- •Defining Methods
- •Using Objects
- •Object Life Cycles
- •Object Creation
- •Object Destruction
- •Assigning to Objects
- •Distinguishing Copying from Assignment
- •The Spreadsheet Class
- •Freeing Memory with Destructors
- •Handling Copying and Assignment
- •Different Kinds of Data Members
- •Static Data Members
- •Const Data Members
- •Reference Data Members
- •Const Reference Data Members
- •More about Methods
- •Static Methods
- •Const Methods
- •Method Overloading
- •Default Parameters
- •Inline Methods
- •Nested Classes
- •Friends
- •Operator Overloading
- •Implementing Addition
- •Overloading Arithmetic Operators
- •Overloading Comparison Operators
- •Building Types with Operator Overloading
- •Pointers to Methods and Members
- •Building Abstract Classes
- •Using Interface and Implementation Classes
- •Building Classes with Inheritance
- •Extending Classes
- •Overriding Methods
- •Inheritance for Reuse
- •The WeatherPrediction Class
- •Adding Functionality in a Subclass
- •Replacing Functionality in a Subclass
- •Respect Your Parents
- •Parent Constructors
- •Parent Destructors
- •Referring to Parent Data
- •Casting Up and Down
- •Inheritance for Polymorphism
- •Return of the Spreadsheet
- •Designing the Polymorphic Spreadsheet Cell
- •The Spreadsheet Cell Base Class
- •The Individual Subclasses
- •Leveraging Polymorphism
- •Future Considerations
- •Multiple Inheritance
- •Inheriting from Multiple Classes
- •Naming Collisions and Ambiguous Base Classes
- •Interesting and Obscure Inheritance Issues
- •Special Cases in Overriding Methods
- •Copy Constructors and the Equals Operator
- •The Truth about Virtual
- •Runtime Type Facilities
- •Non-Public Inheritance
- •Virtual Base Classes
- •Class Templates
- •Writing a Class Template
- •How the Compiler Processes Templates
- •Distributing Template Code between Files
- •Template Parameters
- •Method Templates
- •Template Class Specialization
- •Subclassing Template Classes
- •Inheritance versus Specialization
- •Function Templates
- •Function Template Specialization
- •Function Template Overloading
- •Friend Function Templates of Class Templates
- •Advanced Templates
- •More about Template Parameters
- •Template Class Partial Specialization
- •Emulating Function Partial Specialization with Overloading
- •Template Recursion
- •References
- •Reference Variables
- •Reference Data Members
- •Reference Parameters
- •Reference Return Values
- •Deciding between References and Pointers
- •Keyword Confusion
- •The const Keyword
- •The static Keyword
- •Order of Initialization of Nonlocal Variables
- •Types and Casts
- •typedefs
- •Casts
- •Scope Resolution
- •Header Files
- •C Utilities
- •Variable-Length Argument Lists
- •Preprocessor Macros
- •How to Picture Memory
- •Allocation and Deallocation
- •Arrays
- •Working with Pointers
- •Array-Pointer Duality
- •Arrays Are Pointers!
- •Not All Pointers Are Arrays!
- •Dynamic Strings
- •C-Style Strings
- •String Literals
- •The C++ string Class
- •Pointer Arithmetic
- •Custom Memory Management
- •Garbage Collection
- •Object Pools
- •Function Pointers
- •Underallocating Strings
- •Memory Leaks
- •Double-Deleting and Invalid Pointers
- •Accessing Out-of-Bounds Memory
- •Using Streams
- •What Is a Stream, Anyway?
- •Stream Sources and Destinations
- •Output with Streams
- •Input with Streams
- •Input and Output with Objects
- •String Streams
- •File Streams
- •Jumping around with seek() and tell()
- •Linking Streams Together
- •Bidirectional I/O
- •Internationalization
- •Wide Characters
- •Non-Western Character Sets
- •Locales and Facets
- •Errors and Exceptions
- •What Are Exceptions, Anyway?
- •Why Exceptions in C++ Are a Good Thing
- •Why Exceptions in C++ Are a Bad Thing
- •Our Recommendation
- •Exception Mechanics
- •Throwing and Catching Exceptions
- •Exception Types
- •Throwing and Catching Multiple Exceptions
- •Uncaught Exceptions
- •Throw Lists
- •Exceptions and Polymorphism
- •The Standard Exception Hierarchy
- •Catching Exceptions in a Class Hierarchy
- •Writing Your Own Exception Classes
- •Stack Unwinding and Cleanup
- •Catch, Cleanup, and Rethrow
- •Use Smart Pointers
- •Common Error-Handling Issues
- •Memory Allocation Errors
- •Errors in Constructors
- •Errors in Destructors
- •Putting It All Together
- •Why Overload Operators?
- •Limitations to Operator Overloading
- •Choices in Operator Overloading
- •Summary of Overloadable Operators
- •Overloading the Arithmetic Operators
- •Overloading Unary Minus and Unary Plus
- •Overloading Increment and Decrement
- •Overloading the Subscripting Operator
- •Providing Read-Only Access with operator[]
- •Non-Integral Array Indices
- •Overloading the Function Call Operator
- •Overloading the Dereferencing Operators
- •Implementing operator*
- •Implementing operator->
- •What in the World Is operator->* ?
- •Writing Conversion Operators
- •Ambiguity Problems with Conversion Operators
- •Conversions for Boolean Expressions
- •How new and delete Really Work
- •Overloading operator new and operator delete
- •Overloading operator new and operator delete with Extra Parameters
- •Two Approaches to Efficiency
- •Two Kinds of Programs
- •Is C++ an Inefficient Language?
- •Language-Level Efficiency
- •Handle Objects Efficiently
- •Use Inline Methods and Functions
- •Design-Level Efficiency
- •Cache as Much as Possible
- •Use Object Pools
- •Use Thread Pools
- •Profiling
- •Profiling Example with gprof
- •Cross-Platform Development
- •Architecture Issues
- •Implementation Issues
- •Platform-Specific Features
- •Cross-Language Development
- •Mixing C and C++
- •Shifting Paradigms
- •Linking with C Code
- •Mixing Java and C++ with JNI
- •Mixing C++ with Perl and Shell Scripts
- •Mixing C++ with Assembly Code
- •Quality Control
- •Whose Responsibility Is Testing?
- •The Life Cycle of a Bug
- •Bug-Tracking Tools
- •Unit Testing
- •Approaches to Unit Testing
- •The Unit Testing Process
- •Unit Testing in Action
- •Higher-Level Testing
- •Integration Tests
- •System Tests
- •Regression Tests
- •Tips for Successful Testing
- •The Fundamental Law of Debugging
- •Bug Taxonomies
- •Avoiding Bugs
- •Planning for Bugs
- •Error Logging
- •Debug Traces
- •Asserts
- •Debugging Techniques
- •Reproducing Bugs
- •Debugging Reproducible Bugs
- •Debugging Nonreproducible Bugs
- •Debugging Memory Problems
- •Debugging Multithreaded Programs
- •Debugging Example: Article Citations
- •Lessons from the ArticleCitations Example
- •Requirements on Elements
- •Exceptions and Error Checking
- •Iterators
- •Sequential Containers
- •Vector
- •The vector<bool> Specialization
- •deque
- •list
- •Container Adapters
- •queue
- •priority_queue
- •stack
- •Associative Containers
- •The pair Utility Class
- •multimap
- •multiset
- •Other Containers
- •Arrays as STL Containers
- •Strings as STL Containers
- •Streams as STL Containers
- •bitset
- •The find() and find_if() Algorithms
- •The accumulate() Algorithms
- •Function Objects
- •Arithmetic Function Objects
- •Comparison Function Objects
- •Logical Function Objects
- •Function Object Adapters
- •Writing Your Own Function Objects
- •Algorithm Details
- •Utility Algorithms
- •Nonmodifying Algorithms
- •Modifying Algorithms
- •Sorting Algorithms
- •Set Algorithms
- •The Voter Registration Audit Problem Statement
- •The auditVoterRolls() Function
- •The getDuplicates() Function
- •The RemoveNames Functor
- •The NameInList Functor
- •Testing the auditVoterRolls() Function
- •Allocators
- •Iterator Adapters
- •Reverse Iterators
- •Stream Iterators
- •Insert Iterators
- •Extending the STL
- •Why Extend the STL?
- •Writing an STL Algorithm
- •Writing an STL Container
- •The Appeal of Distributed Computing
- •Distribution for Scalability
- •Distribution for Reliability
- •Distribution for Centrality
- •Distributed Content
- •Distributed versus Networked
- •Distributed Objects
- •Serialization and Marshalling
- •Remote Procedure Calls
- •CORBA
- •Interface Definition Language
- •Implementing the Class
- •Using the Objects
- •A Crash Course in XML
- •XML as a Distributed Object Technology
- •Generating and Parsing XML in C++
- •XML Validation
- •Building a Distributed Object with XML
- •SOAP (Simple Object Access Protocol)
- •. . . Write a Class
- •. . . Subclass an Existing Class
- •. . . Throw and Catch Exceptions
- •. . . Read from a File
- •. . . Write to a File
- •. . . Write a Template Class
- •There Must Be a Better Way
- •Smart Pointers with Reference Counting
- •Double Dispatch
- •Mix-In Classes
- •Object-Oriented Frameworks
- •Working with Frameworks
- •The Model-View-Controller Paradigm
- •The Singleton Pattern
- •Example: A Logging Mechanism
- •Implementation of a Singleton
- •Using a Singleton
- •Example: A Car Factory Simulation
- •Implementation of a Factory
- •Using a Factory
- •Other Uses of Factories
- •The Proxy Pattern
- •Example: Hiding Network Connectivity Issues
- •Implementation of a Proxy
- •Using a Proxy
- •The Adapter Pattern
- •Example: Adapting an XML Library
- •Implementation of an Adapter
- •Using an Adapter
- •The Decorator Pattern
- •Example: Defining Styles in Web Pages
- •Implementation of a Decorator
- •Using a Decorator
- •The Chain of Responsibility Pattern
- •Example: Event Handling
- •Implementation of a Chain of Responsibility
- •Using a Chain of Responsibility
- •Example: Event Handling
- •Implementation of an Observer
- •Using an Observer
- •Chapter 1: A Crash Course in C++
- •Chapter 3: Designing with Objects
- •Chapter 4: Designing with Libraries and Patterns
- •Chapter 5: Designing for Reuse
- •Chapter 7: Coding with Style
- •Chapters 8 and 9: Classes and Objects
- •Chapter 11: Writing Generic Code with Templates
- •Chapter 14: Demystifying C++ I/O
- •Chapter 15: Handling Errors
- •Chapter 16: Overloading C++ Operators
- •Chapter 17: Writing Efficient C++
- •Chapter 19: Becoming Adept at Testing
- •Chapter 20: Conquering Debugging
- •Chapter 24: Exploring Distributed Objects
- •Chapter 26: Applying Design Patterns
- •Beginning C++
- •General C++
- •I/O Streams
- •The C++ Standard Library
- •C++ Templates
- •Integrating C++ and Other Languages
- •Algorithms and Data Structures
- •Open-Source Software
- •Software-Engineering Methodology
- •Programming Style
- •Computer Architecture
- •Efficiency
- •Testing
- •Debugging
- •Distributed Objects
- •CORBA
- •XML and SOAP
- •Design Patterns
- •Index
A Crash Course in C++
bool AirlineTicket::getHasEliteSuperRewardsStatus()
{
return (fHasEliteSuperRewardsStatus);
}
void AirlineTicket::setHasEliteSuperRewardsStatus(bool inStatus)
{
fHasEliteSuperRewardsStatus = inStatus;
}
The preceding example exposes you to the general syntax for creating and using classes. Of course, there is much more to learn. Chapters 8 and 9 go into more depth about the specific C++ mechanisms for defining classes.
Your First Useful C++ Program
The following program builds on the employee database example used earlier when discussing structs. This time, you will end up with a fully functional C++ program that uses many of the features discussed in this chapter. This real-world example includes the use of classes, exceptions, streams, arrays, namespaces, references, and other language features.
An Employee Records System
A program to manage a company’s employee records needs to be flexible and have useful features. The feature set for this program includes the following.
The ability to add an employee
The ability to fire an employee
The ability to promote an employee
The ability to view all employees, past and present
The ability to view all current employees
The ability to view all former employees
The design for this program divides the code into three parts. The Employee class encapsulates the information describing a single employee. The Database class manages all the employees of the company. A separate UserInterface file provides the interactivity of the program.
The Employee Class
The Employee class maintains all the information about an employee. Its methods provide a way to query and change that information. Employees also know how to display themselves on the console. Methods also exist to adjust the employee’s salary and employment status.
29
Chapter 1
Employee.h
The Employee.h file declares the behavior of the Employee class. The sections of this file are described individually in the material that follows.
// Employee.h
#include <iostream>
namespace Records {
The first few lines of the file include a comment indicating the name of the file and the inclusion of the stream functionality.
This code also declares that the subsequent code, contained within the curly braces, will live in the Records namespace. Records is the namespace that is used throughout this program for applicationspecific code.
const int kDefaultStartingSalary = 30000;
This constant, representing the default starting salary for new employees, lives in the Records namespace. Other code that lives in Records can access this constant simply as kDefaultStartingSalary. Elsewhere, it must be referenced as Records::kDefaultStartingSalary.
class Employee
{
public: |
|
|
|
Employee(); |
|
|
|
void |
promote(int inRaiseAmount = 1000); |
||
void |
demote(int inDemeritAmount = 1000); |
||
void |
hire(); |
// Hires or rehires the employee |
|
void |
fire(); |
// Dismisses the employee |
|
void |
display(); |
// Outputs employee info to the console |
|
// Accessors and setters |
|||
void |
|
setFirstName(std::string inFirstName); |
|
std::string |
getFirstName(); |
||
void |
|
setLastName(std::string inLastName); |
|
std::string |
getLastName(); |
||
void |
|
setEmployeeNumber(int inEmployeeNumber); |
|
int |
|
getEmployeeNumber(); |
|
void |
|
setSalary(int inNewSalary); |
|
int |
|
getSalary(); |
|
bool |
|
getIsHired(); |
The Employee class is declared, along with its public methods. The promote() and demote() methods both have integer parameters that are specified with a default value. In this way, other code can omit the integer parameters and the default will automatically be used.
30
A Crash Course in C++
A number of accessors provide mechanisms to change the information about an employee or query the current information about an employee:
private:
std::string mFirstName; std::string mLastName;
int mEmployeeNumber;
int mSalary; bool fHired;
};
}
Finally, the data members are declared as private so that other parts of the code cannot modify them directly. The accessors provide the only public way of modifying or querying these values.
Employee.cpp
The implementations for the Employee class methods are shown here:
// Employee.cpp
#include <iostream>
#include “Employee.h”
using namespace std;
namespace Records {
Employee::Employee()
{
mFirstName = “”; mLastName = “”; mEmployeeNumber = -1;
mSalary = kDefaultStartingSalary; fHired = false;
}
The Employee constructor sets the initial values for the Employee’s data members. By default, new employees have no name, an employee number of -1, the default starting salary, and a status of not hired.
void Employee::promote(int inRaiseAmount)
{
setSalary(getSalary() + inRaiseAmount);
}
void Employee::demote(int inDemeritAmount)
{
setSalary(getSalary() - inDemeritAmount);
}
31
Chapter 1
The promote() and demote() methods simply call the setSalary() method with a new value. Note that the default values for the integer parameters do not appear in the source file. They only need to exist in the header.
void Employee::hire()
{
fHired = true;
}
void Employee::fire()
{
fHired = false;
}
The hire() and fire() methods just set the fHired data member appropriately.
void Employee::display()
{
cout << “Employee: “ << getLastName() << “, “ << getFirstName() << endl; cout << “-------------------------” << endl;
cout << (fHired ? “Current Employee” : “Former Employee”) << endl; cout << “Employee Number: “ << getEmployeeNumber() << endl;
cout << “Salary: $” << getSalary() << endl; cout << endl;
}
The display() method uses the console output stream to display information about the current employee. Because this code is part of the Employee class, it could access data members, such as mSalary, directly instead of using the getSalary() accessor. However, it is considered good style to make use of accessors when they exist, even within the class.
// Accessors and setters
void Employee::setFirstName(string inFirstName)
{
mFirstName = inFirstName;
}
string Employee::getFirstName()
{
return mFirstName;
}
void Employee::setLastName(string inLastName)
{
mLastName = inLastName;
}
string Employee::getLastName()
{
return mLastName;
}
32
A Crash Course in C++
void Employee::setEmployeeNumber(int inEmployeeNumber)
{
mEmployeeNumber = inEmployeeNumber;
}
int Employee::getEmployeeNumber()
{
return mEmployeeNumber;
}
void Employee::setSalary(int inSalary)
{
mSalary = inSalary;
}
int Employee::getSalary()
{
return mSalary;
}
bool Employee::getIsHired()
{
return fHired;
}
}
A number of accessors and setters perform the simple task of getting and setting values. Even though these methods seem trivial, it’s better to have trivial accessors and setters than to make your data members public. In the future, you may want to perform bounds checking in the setSalary() method, for example.
EmployeeTest.cpp
As you write individual classes, it is often useful to test them in isolation. The following code includes a main() function that performs some simple operations using the Employee class. Once you are confident that the Employee class works, you should remove or comment-out this file so that you don’t attempt to compile your code with multiple main() functions.
// EmployeeTest.cpp
#include <iostream>
#include “Employee.h”
using namespace std; using namespace Records;
int main (int argc, char** argv)
{
cout << “Testing the Employee class.” << endl;
33