使用指针遍历数组的for循环无法正常工作

Question

For my homework problem I must use pointers to traverse arrays. When I try to store 3 "name" values into member variables of an array of an Object called RentalAgency , I find that it stores the value, but never increments. Therefore the last value given is stored in the first index and the next two are empty.

RentalAgency *agencies_ptr = agencies;

for(int i = 0; i < 3;i++,++agencies_ptr){
    infile.get((agencies->name),MAX_SIZE,space);
}

Where agencies is an array of Objects

If the input is Hertz, Alamo, and Budget, it should output Hertz, Alamo, and Budget. The actual output is just Budget.

Answer 1

Just write

for(int i = 0; i < 3; i++){
    infile.get( agencies_ptr[i].name, MAX_SIZE, space );
}

Answer 2

You are desreferencing agencies , not agencies_ptr (and the parenthesis are not needed):

RentalAgency *agencies_ptr = agencies;

for(int i = 0; i < 3; ++i, ++agencies_ptr)
   infile.get(agencies_ptr->name, MAX_SIZE, space);

But a more idiomatic way of traversing a "range" is this ( it stands for iterator ):

RentalAgency *agencies_it = agencies;
RentalAgency *agencies_end = agencies_it + 3;

for(; agencies_it != agencies_end; ++agencies_it)
   infile.get(agencies_it->name, MAX_SIZE, space);

It's cleaner, express intent better and is more familiar to see among experienced programmers.