How to stop addObject from overwriting all previous objects in a NSMutableArray - objective-c

Question

addObject is overwriting all the previous cells. So if the array is size 4, adding the objects increases the size, but it also overwrites all other cells with the same thing.
groups = [[NSMutableArray alloc]init];
[groups addObject:[[Group alloc] init]];
[[groups objectAtIndex:0] setGroupName:#"cs480"];
[[groups objectAtIndex:0] setPassword:#"apple1"];
[groups addObject:[[Group alloc] init]];
[[groups objectAtIndex:1] setGroupName:#"cs481"];
[[groups objectAtIndex:1] setPassword:#"apple2"];
+(void) print{
NSLog(#"size: %lu",(unsigned long)[groups count]);
for(int i = 0; i < [groups count]; i++){
Group *group = [groups objectAtIndex:i];
NSLog(#"%#\t%#\n",[group getGroupName], [group getPassword]);
}
}
The group class is
#import <Foundation/Foundation.h>
#import "Group.h"
#import "Person.h"
#import "Pie.h"
#implementation Group
NSString* groupName;
NSString* password;
NSMutableArray *groupMembers;
NSMutableArray *skillsOfMembers;
-(id) init{
self = [super init];
if(self){
NSLog(#"inside group constructor");
groupMembers = [[NSMutableArray alloc] init];
skillsOfMembers = [[NSMutableArray alloc] init];
groupName = [[NSString alloc]init];
password = [[NSString alloc]init];
}
return self;
}
-(NSInteger) authenticate:(NSString *)checkGroupName :(NSString *)checkPassword{
if([checkGroupName isEqualToString:groupName]&&[checkPassword isEqualToString:password]){
return 1;
}
return 0;
}
-(void) setGroup:(NSMutableArray*)newGroupMembers{
groupMembers = newGroupMembers;
}
-(NSMutableArray*) getGroup{
return groupMembers;
}
-(Person*) getPerson:(int) index{
return [groupMembers objectAtIndex:index];
}
-(void) setPerson:(int) index :(Person*) newPerson{
Person* person = [groupMembers objectAtIndex:index];
person = newPerson;
}
-(NSMutableArray*) getSkillsOfPerson:(int)index{
return [skillsOfMembers objectAtIndex:index];
}
-(void) setSkillsOfPerson:(Pie*) newSkills :(int)index{
Pie *skillsOfMember = [skillsOfMembers objectAtIndex:index];
skillsOfMember = newSkills;
}
-(void) setGroupName:(NSString*) newName{
groupName = [newName copy];
}
-(NSString*) getGroupName{
return groupName;
}
-(void) setPassword:(NSString*) newPassword{
password = [newPassword copy];
}
-(NSString*) getPassword{
return password;
}
#end
The output is
2014-11-10 13:23:19.013 Balanced Team Pie[1964:66289] size: 2
2014-11-10 13:23:19.013 Balanced Team Pie[1964:66289] cs481 apple2
2014-11-10 13:23:19.014 Balanced Team Pie[1964:66289] cs481 apple2
What is the issue?

Answer 1

These:
#implementation Group
NSString* groupName;
NSString* password;
NSMutableArray *groupMembers;
NSMutableArray *skillsOfMembers;
are not instance variables. They are just global variables. They are declared at file scope. The fact that they come between #implementation and its corresponding #end means nothing to the compiler.
Effectively, there's one set of variables for the whole program, rather than one set of variables for each instance of the Group class.
You probably meant:
#implementation Group
{
NSString* groupName;
NSString* password;
NSMutableArray *groupMembers;
NSMutableArray *skillsOfMembers;
}
The curly braces are required to make the variables instance variables.