Classes Class Data Members & Initializers

Department of Computer and Information Science,School of Science, IUPUI ClassesClass Data Members & Initializers CSCI 240 Dale Roberts, Lecturer Computer Science, IUPUI E-mail: droberts@cs.iupui.edu

Class Objects as Members -- Example • class student{ char *name; public: student(char *ip) { name = new char[50]; strcpy(name, ip); } ~student(){delete[] name;} };

Class Objects as Members -- Example • class instructor{ char *name; public: instructor(char *ip) { name = new char[50]; strcpy(name, ip); } ~instructor(){delete[] name;} };

Class Objects as Members -- Example • class csci_c{ student s1, s2; instructor i1; char *location; public: //Constructor Initializer csci_c(char *n1, char *n2, char *n3, char *l) :s1(n1), s2(n2), i1(n3){ location = new char[50]; strcpy(location, l); } ~csci_c(){delete[] location;} }; • main() { csci_c fall_class("John","Tom","Henry","SI102");}

Class Objects as Data Members • Data Members can be User Defined Types Having their Constructors • Constructor Initializer is Used • Appropriate Constructors are Invoked on the Order they are Specified in the Class Declaration • Destructor of the Class Containing Members of Other Classes is Called First, Followed by the Member's Destructors in Reverse Order of Declaration

Constructor Initializer • Specifies the Processing to be Performed Before the Actual Constructor Processing Starts • A List of Entries, Each of Which has: • Identifier of Fundamental Data Type • Identifier of a Class Object • Name of a Base Class -- Inheritance • Each Name is Followed by Its Initialization Values in Parenthesis • Appropriate Constructors are Invoked

Constructor Initializer -- Example • /* Assume the Previous Definitions of Classes "student" and "instructor" are Valid */ class csci_c{ student s1, s2; instructor i1; char *location; int capacity; public: /* Constructor Initializer */ csci_c(char *n1,char *n2,char *n3,char *l,int c) :s1(n1), s2(n2), i1(n3), location(l), capacity(c){} ~csci_c(){} }; • main() { csci_c summer("John","Tom","Henry","SL110",20); }

Array of Class Objects -- A Class With a Constructor • Default Constructor is MUST • All the Objects will be Initialized as per the Default Constructor • You can use array initializers to pass a single argument to a constructor of a declared array • There is NO Way to pass an argument to a constructors of a Dynamic Array Declaration • Destructor MUST be Called for EACH ELEMENT in the Array • Automatic Array Objects -- Implicit Destruction • Explicitly Created Objects by new -- delete[] Operator

Array of Objects -- Example • #define size 50 • class student{ char *name; public: student() //Default Constructor {name = new char[size]; strcpy(name, "No Name");} student (char *ip): name(ip){} ~student(){delete[] name;} };

Array of Objects -- Example • main(){ /* object array of "student" class all initialized to "No Name" – default constructor */ student s1[size]; /* Initialization -- second constructor */ student s2[2] = {"John", "Tom"}; /* Dynamically created array -- default constructor */ student *s3 = new student[3]; /* Dynamically created object -- default constructor */ student *s4 = new student; /* "s1" and "s2" arrays will be automatically destroyed when "main“ exits. However, array pointed by "s3" and object pointed by "s4", must be deleted. */ delete[] s3; delete s4;}

Acknowledgements • These slides were originally prepared by Rajeev Raje, modified by Dale Roberts.

Classes Class Data Members & Initializers