Objective-C Struct problems -

i have student structure provides 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 grades structure provides 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, have main function 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 ssetgrades (&stu, @"5 - 90 85 95.5 77.5 88") line in main, freezes , says program has stopped working. guesses why , if so, how can fix error?

note: done in notepad++ on windows 7

your primary issue definition of student structure. change grades reference isn't pointer:

struct student {     nsstring *myname;     struct grades mygrades; }; 

the problem pointer never initialize pointer. removing pointer memory issues causing crash go away.

as result of change, need change few other things. call setgrades needs pass address of mygrades:

setgrades(&(s->mygrades), gradelist); 

even better replace of struct/function code actual classes.