C：通过引用传递struct

Question

I've defined the following struct:

typedef struct {
    double salary;
} Employee;

I want to change the value of salary . I attempt to pass it by reference, but the value remains unchanged. Below is the code:

void raiseSalary (Employee* e, double newSalary) {
    Employee myEmployee = *e;
    myEmployee.salary = newSalary;
}

When I call this function, the salary remains unchanged. What am I doing wrong?

Answer 1

You're passing a pointer to the original, but then you create a copy of it:

Employee myEmployee =*e;

creates a copy.

e->salary = newSalary;

will do it. Or, if you must have an auxiliary variable for whatever reasons:

Employee* myEmployee =e;
Myemployee->salary= newSalary;

This way, both variables will point to the same object.

Answer 2

void raiseSalary(Employee* e, double newSalary){
    e->salary= newSalary;
    }

In your code you create a local copy of the struct and only this local copy is changed.

Answer 3

假设你已经在调用者处分配了内存，它应该是：

e->salary= newSalary;