Teach Yourself Borland C++ in 14 Days - portal

Up to Your Neck in C++
Figure 3.1.
A pointer to an object
in memory. mailingListRecord*
listArray
Let’s go back to a code snippet you saw earlier:
mailingListRecord* listArray;
listArray = new mailingListRecord;
strcpy(listArray->firstName, “Ian”);
strcpy(listArray->lastName, “Spencer”);
// etc.
On the third line you see that the firstName data member of the structure is accessed using
the indirect member operator (->) rather than the structure member operator. (We discussed
the structure member operator yesterday in the section titled “Structures.” The term direct
member operator is also used and is more representative than structure member operator, so
I will use direct member operator from now on.) When you create an object dynamically, you
must access the object’s data members and functions using this operator.
Creating an array of structures dynamically requires a bit more work. Again, here’s the stackbased
version:
mailingListRecord listArray[3];
listArray[0].zip = 57441;
And the dynamic version:
stack memory
listArray
listArray points to
address 0x00780E50,
which is an instance
of the mailingListRecord
structure in memory
mailingListRecord* listArray[3];
for (int i=0;izip = 57441;
mailingListRecord
structure in memory
heap memory
0x00780E50
firstName
lastName
address
city
state
zip
Note that I have to create a new instance of the structure for each element of the array. Notice
also that to access a data member of the array, I use the indirect membership operator
combined with the subscript operator.
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