Destructors

A destructor is another type of special member function. The name of the destructor for a class is the tilde character (~) followed by the class name. This naming convention has intuitive appeal, because as we will see in a later chapter, the tilde operator is the bitwise complement operator, and, in a sense, the destructor is the complement of the constructor. Note that a destructor is often referred to with the abbreviation "dtor" in the literature. We prefer not to use this abbreviation.

A class's destructor is called implicitly when an object is destroyed. This occurs, for example, as an automatic object is destroyed when program execution leaves the scope in which that object was instantiated. The destructor itself does not actually release the object's memoryit performs termination housekeeping before the system reclaims the object's memory, so the memory may be reused to hold new objects.

A destructor receives no parameters and returns no value. A destructor may not specify a return typenot even void. A class may have only one destructordestructor overloading is not allowed.

Common Programming Error 9.3

It is a syntax error to attempt to pass arguments to a destructor, to specify a return type for a destructor (even void cannot be specified), to return values from a destructor or to overload a destructor.

Even though destructors have not been provided for the classes presented so far, every class has a destructor. If the programmer does not explicitly provide a destructor, the compiler creates an "empty" destructor. [Note: We will see that such an implicitly created destructor does, in fact, perform important operations on objects that are created through composition (Chapter 10) and inheritance (Chapter 12).] In Chapter 11, we will build destructors appropriate for classes whose objects contain dynamically allocated memory (e.g., for arrays and strings) or use other system resources (e.g., files on disk, which we study in Chapter 17). We discuss how to dynamically allocate and deallocate memory in Chapter 10.


Software Engineering Observation 9.11

As we will see in the remainder of the book, constructors and destructors have much greater prominence in C++ and object-oriented programming than is possible to convey after only our brief introduction here.



Introduction to Computers, the Internet and World Wide Web

Introduction to C++ Programming

Introduction to Classes and Objects

Control Statements: Part 1

Control Statements: Part 2

Functions and an Introduction to Recursion

Arrays and Vectors

Pointers and Pointer-Based Strings

Classes: A Deeper Look, Part 1

Classes: A Deeper Look, Part 2

Operator Overloading; String and Array Objects

Object-Oriented Programming: Inheritance

Object-Oriented Programming: Polymorphism

Templates

Stream Input/Output

Exception Handling

File Processing

Class string and String Stream Processing

Web Programming

Searching and Sorting

Data Structures

Bits, Characters, C-Strings and structs

Standard Template Library (STL)

Other Topics

Appendix A. Operator Precedence and Associativity Chart

Appendix B. ASCII Character Set

Appendix C. Fundamental Types

Appendix D. Number Systems

Appendix E. C Legacy Code Topics

Appendix F. Preprocessor

Appendix G. ATM Case Study Code

Appendix H. UML 2: Additional Diagram Types

Appendix I. C++ Internet and Web Resources

Appendix J. Introduction to XHTML

Appendix K. XHTML Special Characters

Appendix L. Using the Visual Studio .NET Debugger

Appendix M. Using the GNU C++ Debugger

Bibliography



C++ How to Program
C++ How to Program (5th Edition)
ISBN: 0131857576
EAN: 2147483647
Year: 2004
Pages: 627

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