从新创建的对象指针正确调用方法

Question

I am a Java programmer who is taking a C++ class. I can successfully create my object on the stack by not using the "new" keyword.

SeatSelection premium(1,5);
premium.toString();

That code runs my toString() method correctly.

I am also attempting to create a new C++ object using the "new" keyword and then attempting to run the toString() method.

SeatSelection *premium = new SeatSelection(1,5);

I don't know the proper syntax for calling my toString() method.

What I have tried

premium.toString();     //doesn't compile, premium is of non-class type "SeatSelection*"

What is the syntax for calling a method using a object pointer?

Answer 1

Use operator -> Along with . (dot) it is so-called class member access operator.

For example

SeatSelection *premium = new SeatSelection(1,5);
premium->toString();

Or you can write

SeatSelection *premium = new SeatSelection(1,5);
( *premium ).toString();

According to the C++ Standard

expression E1->E2 is converted to the equivalent form (*(E1)).E2;

Answer 2

In C++ anytime you use new you are creating an object on the heap and getting a pointer to that object in return.

In C++ there are two ways to deference a pointer.

1) Use an asterisk as in (*premium) , then use a dot operator to call a function on that class (ie (*premium).toString(); ).

2) Use the arrow -> operator as suggested in other examples, which merges the functionality of the asterisk and dot in one fell swoop and "looks prettier" (ie premium->toString(); ).

DON'T FORGET C++ is NOT garbage collected like Java , so when you new up a class, you must have a matching delete , or you will be hemorrhaging memory.