Part V: Optional Features in Visual Studio .NET

Print PDF417 in Visual Studio .NET Part V: Optional Features

// output using index cout << To test index: students[3456] = << students[3456]->display() << endl; if (students[0123] == NULL) { cout << but students[0123] returns a NULL << endl; } system( PAUSE ); return 0; }

The key to the program (if you can pardon the pun) is found in the initial three typedefs A map contains a set of Pair objects, each of which contains a first and second element The first element is the student ID key, and the second is the Student object The Map class adds an object of class SC This class con tains a single method that compares two Student objects to determine which is larger (This is slightly more complicated than the global function used with the list collection, but the effect is the same) The STLMap program begins by creating three Student Pair objects and adding them to the list The iteration through the container displays the Student objects in order by student ID There is no need to invoke a sort() method because map classes already retain objects sorted by key The second section of the STLMap program looks up a student by ID using the find() method The program also demonstrates how easy it is to retrieve the prior and next objects in the list using the decrement and increment operators The output from the program appears as follows:

Look up student 3456 Found student 3456 - Sean Yours Predecessor = 1234 - Fresch Man Successor = 5678 - Student, Jr The call studentsfind(0123) returns studentsend() since student 0123 doesn t exist To test index: students[3456] = 3456 - Sean Yours but students[0123] returns a NULL Press any key to continue

TEAM LinG - Live, Informative, Non-cost and Genuine!

TEAM LinG - Live, Informative, Non-cost and Genuine!

hat For Dummies book would be complete without a Part of Tens In 29, I cover ten ways to avoid adding bugs to your C++ program (Most of these suggestions work for C programs too, at no extra charge) 30 lists the ten most important compiler options available in the Dev-C++ compiler, which is available to the reader on the enclosed CD-ROM

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29

Enabling all warnings and error messages Insisting on clean compiles Using a clear and consistent coding style Limiting the visibility Adding comments to your code while you write it Single-stepping every path at least once Avoiding overloaded operators Heap handling Using exceptions to handle errors Avoiding multiple inheritance

n this chapter, I look at several ways to minimize errors, as well as ways to make debugging the errors that are introduced easier

The syntax of C++ allows for a lot of error checking When the compiler encounters a construct that it cannot decipher, it has no choice but to gener ate an error message Although the compiler attempts to sync back up with the next statement, it does not attempt to generate an executable program

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Disabling warning and error messages is a bit like unplugging the Check Engine light on your car dashboard because it bothers you: Ignoring the problem doesn t make it go away If your compiler has a Syntax Check from Hell mode, enable it Both Visual StudioNET and Dev-C++ have an Enable All Messages option set it You save time in the end During all its digging around in your source code, a good C++ compiler also looks for suspicious-looking syntactical constructs, such as the following code snippet:

#include studenth #include MyClassh Student* addNewStudent(MyClass myObject, char *pName, SSNumber ss) { Student* pS; if (pName != 0) { pS = new Student(pName, ss); myObjectaddStudent(pS); } return pS; }

Here you see that the function first creates a new Student object that it then adds to the MyClass object provided (Presumably addStudent() is a member function of MyClass) If a name is provided (that is, pName is not 0), a new Student object is created and added to the class With that done, the function returns the Student cre ated to the caller The problem is that if pName is 0, pS is never initialized to anything A good C++ compiler can detect this path and generate a warning that pS might not be initialized when it s returned to the caller and maybe you should look into the problem, or words to that effect