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Structs vs. Classes

Introduction

• In addition to define a class we can declare a struct.

• struct comes from the C programming language.

  • In C, we create structs as a container for data, much like a record in many other programming languages.

  • C++ also supports struct since it has to be compatible with C.

  • However, it adds the ability to treat structs very much like classes.

• Essentially the same as a class except that members are public by default. (With classes, members are private by default.)

General Guidelines

• struct

  • Use struct for passive objects with public access

  • Don't declare methods in struct

• class

  • Use class for active objects with complex behavior an private access

  • Implement getters/setters as needed

  • Implement member methods as needed

• These guidelines are very general. But, remember! Other C++ programmers will likely be modifying and extending your code. So, don't use C++ in a way that's very different from what C++ programmers expect. For example, don't use a struct and then make everything in the struct so it behaves like a class, just use a class instead.

Examples

• Class

  xxxxxxxxxx
  10
  1
  class Person
  2
  {
  3
      // Members are private by default
  4
      std::string name;
  5
      std::string get_name();
  6
  };
  7
  
  8
  Person p;
  9
  p.name = "Jack";            // Compiler ERROR - private
  10
  std::cout << p.get_name();  // Compiler ERROR - private
  

• Struct

  xxxxxxxxxx
  10
  1
  struct Person
  2
  {
  3
      // Members are public by default
  4
      std::string name;
  5
      std::string get_name(); 
  6
  };
  7
  
  8
  Person p;
  9
  p.name = "Jack";            // OK - public
  10
  std::cout << p.get_name();  // OK - public