Classes Class Data Members & Initializers Department of Computer and Information Science, School of Science, IUPUI CSCI 240 Classes Class Data Members & Initializers Dale Roberts, Lecturer Computer Science, IUPUI E-mail: droberts@cs.iupui.edu 8/29/2019

Class Objects as Members -- Example class student{ char *name; public: student(char *ip) { name = new char[50]; strcpy(name, ip); } ~student(){delete[] name;} }; 8/29/2019

Class Objects as Members -- Example class instructor{ char *name; public: instructor(char *ip) { name = new char[50]; strcpy(name, ip); } ~instructor(){delete[] name;} }; 8/29/2019

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");} 8/29/2019

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 8/29/2019

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 8/29/2019

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); } 8/29/2019

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 8/29/2019

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;} }; 8/29/2019

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; } 8/29/2019

Acknowledgements These slides were originally prepared by Rajeev Raje, modified by Dale Roberts. 8/29/2019