Objective-C Struct problems - objective-c

Question

I have a student structure that provides the following code:
#import <Foundation/Foundation.h>
#import "Grades.m"
#import <stdio.h>
struct Student
{
NSString *myName;
struct Grades *myGrades;
};
void setName(struct Student *s, NSString *name);
void ssetGrades(struct Student *s, NSString *gradeList);
void setName(struct Student *s, NSString *name)
{
s->myName = name;
}
void ssetGrades(struct Student *s, NSString *gradeList)
{
printf("\n\nWorking\n\n");
setGrades(s->myGrades, gradeList);
printf("\n\nWorking");
}
I have a grades structure that provides the following:
#import <stdio.h>
#import <Foundation/Foundation.h>
#define null NULL
struct Grades
{
double sgrades[100];
int length;
};
void setGrades(struct Grades *grades, NSString *gradeList);
void setGrade(int spot, double grade, struct Grades *grades);
void setGrades(struct Grades *grades, NSString *gradeList)
{
NSString *a = [gradeList substringToIndex:1];
NSString *b = [gradeList substringWithRange:NSMakeRange(3, 19)];
int ln = [a integerValue];
grades->length = ln;
double grade;
int x = 1;
int prev = 1;
int y;
int z = 0;
for(y=0;y<ln;y++)
{
while(x < [b length] && [b characterAtIndex:x] != ' ')
{
z++;
x++;
}
NSString *sub = [b substringWithRange:NSMakeRange(prev, z)];
grade = [sub doubleValue];
printf("%d %d %d %lf\n", y, prev, z, grade);
prev += z+1;
x++;
z=0;
setGrade(y, grade, grades);
}
}
void setGrade(int spot, double grade, struct Grades *grades)
{
grades->sgrades[spot] = grade;
}
And finally, I have a main function with the following:
#import <Foundation/Foundation.h>
#import "Grades.m"
#import "Student.m"
#import <stdio.h>
int main (int argc, const char * argv[])
{
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
struct Grades test;
setGrades(&test, #"5 - 90 85 95.5 77.5 88");
toString(&test);
printf("\nsum = %lf", getSum(&test));
printf("\nnum grades = %d", getNumGrades(&test));
printf("\nlow grade = %lf", getLowGrade(&test));
printf("\nhigh grade = %lf", getHighGrade(&test));
struct Student stu;
setName(&stu, #"Billy Bob");
ssetGrades(&stu, #"5 - 90 85 95.5 77.5 88");
[pool release];
return 0;
}
Now whenever I get to the ssetGrades (&stu, #"5 - 90 85 95.5 77.5 88") line in the main, it freezes up and says that the program has stopped working. Any guesses why and if so, how can I fix this error?
NOTE: This is all done in Notepad++ on Windows 7

Answer 1

Your primary issue is your definition of your Student structure. Change the Grades reference so it isn't a pointer:
struct Student
{
NSString *myName;
struct Grades myGrades;
};
The problem with the pointer is that you never initialize the pointer. By removing the pointer the memory issues causing the crash will go away.
As a result of this change, you need to change a few other things. The call to setGrades needs to pass the address of myGrades:
setGrades(&(s->myGrades), gradeList);
Even better would be to replace all of this struct/function code with actual classes.