Structures or Records

• This is a complex type from c.
• But it has been modified in c++.
• We will use a structure to group data fields into a single item.
  • Consider a card
  • It has a suit (heart, spade, club, diamond)
  • It also has a value (1-13)
• We could use two variables to describe a card, but this is not convenient.
• So a structure will be the ideal container.
• Declaring a structure
  • Much like functions structures must be declared before they can be used..
  • This is done either at the the top of the program or in a .h file.
• The card structure

  • struct CardT {
       SuitT suit;
       int value;
    };
           

  • In this case, suit and value are examples of fields or members.
    • Each field has a type.
    • Each field has an associated identifier.
  • Note when we are declaring a structure, we are defining what it will look like.
  • We are note declaring a variable of that type.
  • No memory has been allocated.
• Look at CardT.h
• Declaring an instance of a structure
  • Just like anything else

  • int i;
    SuitT suit;
    CardT card1;  // declare with default initialization if any
    CardT card2{SuiteT::DIAMOND, 11};   // declare and initialize with values.
    CardT card3{RandomCard()}; // declare and initialize with function call.
           

  • This allocates memory.
• To access the individual fields of a structure you use the member selector a dot (.)

  • card1.suit = SuitT::HEART;
    card1.value = 2;
           

• Structures have no default I/O, so you must write this.
  • I usually follow the enumerator pattern and provide a to string function.
  • Look at CardTToString in CardT.cpp
• Structures do not directly support math.
• Structures do not directly support comparison.
• Structures can be passed to functions as variable or value parameters.
• Structures can be the return type of a function.
• Look at cardTest.cpp