CPP Arrays and the Free Store

Using objects in arrays

  • Any object, whether built-in or user defined, can be stored in an array.
  • Accessing member data in an array of objects is a two-step process.
    1. Identify the member of the array by using the index operator ([ ]).
    2. Add the member operator (.) to access the particular member variable.
    Cow Farm[6];
    int i;
    for (i = 0; i < 6; i++){
    // The Farm[i] returns the object of a Cow
       Farm[i].setAge(2*i +1);

Declaring Arrays on the Free Store.

  • As for any object, you can declare an array of object on the free store with the new keyword.
    Cow *pFarm = new Cow[500];  // pFarm is a pointer to an array of 500 Cow objects
    Cow *pCow = pFarm;          // pCow points to pFarm[0]
    pCow->setAge(10);           // set pFarm[0] to 10
    pCow++;                     // advance to pFarm[1]
    pCow->setAge(20);           // set pFarm[1] to 20
  • Be aware of that:
    Cow   pOne[50];             // Is an array of 50 Cow objects
    Cow * pTwo[50];             // Is an array of 50 pointers to Cow objects
    Cow * pThree = new Cow[50]; // Is a pointer to an array of 50 Cow objects
    Please remember that pOne and pThree have instances of Cow, but pTwo is only an array with no Cow object instance.
  • You find an program example in the Aggregation and Delegation session.
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