程序设计基石与实践之使用构造函数初始化对象

预备知识

每一个类都可以提供一个构造函数,用于类对象创建时的初始化.构造函数是一种特殊的成员函数,定义时必须和类同名,这样编译器才能够将它和类的其他成员函数区分开来.构造函数各其他函数之间的一个重大差别是构造函数不能返回值,因此对它们不可以指定返回类型.通常情况下,构造函数声明为public.

UML图如下所示:

程序如下所示:

// Instantiating multiple objects of the GradeBook class and using the GradeBook constructor to specify the course name // when each GradeBook object is created.#include <iostream>using std::cout; using std::endl;#include <string> // program uses C++ standard string classusing std::string;// GradeBook class definitionclass GradeBook{public:   // constructor initializes courseName with string supplied as argument   GradeBook( string name )   {      setCourseName( name ); // call set function to initialize courseName   } // end GradeBook constructor   // function to set the course name   void setCourseName( string name )   {      courseName = name; // store the course name in the object   } // end function setCourseName   // function to get the course name   string getCourseName()   {      return courseName; // return object's courseName   } // end function getCourseName   // display a welcome message to the GradeBook user   void displayMessage()   {      // call getCourseName to get the courseName      cout << "Welcome to the grade book for\n" << getCourseName()           << "!" << endl;   } // end function displayMessageprivate:   string courseName; // course name for this GradeBook}; // end class GradeBook  // function main begins program executionint main(){   // create two GradeBook objects   GradeBook gradeBook1( "Introduction to C++ Programming" );   GradeBook gradeBook2( "Data Structures in C++" );   // display initial value of courseName for each GradeBook   cout << "gradeBook1 created for course: " << gradeBook1.getCourseName()      << "\ngradeBook2 created for course: " << gradeBook2.getCourseName()       << endl;   return 0; // indicate successful termination} // end main

测试输出

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