Question

I have a structured defined as

typedef struct{
char string1
char string2
int number1
char string3
}structure1

and want to assign the values to string1,string2,number1,string3 in a loop like this

structure1 bob
for(int i = 0,i<=4,i++)
{
bob.i = assigned value
}

now I understand that code above in it’s generic form will only work for integers as you can’t just go string = string for assignment, but the same problem arises as I don’t know how to reference the values inside a struct without specifically naming them one by one. for strings there will be a second assignment relying on the i index to work out if it’s a integer or string at the time so it can perform the assignment. I was thinking something along the lines of enum’s but I’ve never used them in a practical sense before, just theoretical.

Answer 1

It’s not possible in C. The closest to that would be calculating field offsets and then using them to assign values:

int fieldOffset[4];

structure1 base;

fieldOffset[0] = (char*)&base.string1 - (char*)&base;
fieldOffset[1] = (char*)&base.string2 - (char*)&base;
fieldOffset[2] = (char*)&base.number1 - (char*)&base;
fieldOffset[3] = (char*)&base.string3 - (char*)&base;

structure1 structYouWantToAssign;

for (int i = 0; i < 4; ++i)
{
    *((char*)&structYouWantToAssign + fieldOffset[i]) = assignedValue;
}

Warning: this code is just to demonstrate it is possible to assign fields without their name, but you should not use it!