NSMutableArray: add and extract struct - objective-c

Question

I'm trying to store some data in an NSMutableArray. This is my struct:
typedef struct{
int time;
char name[15];
}person;
This is the code to add a person:
person h1;
h1.time = 108000;
strcpy(h1.name, "Anonymous");
[highscore insertObject:[NSValue value:&h1 withObjCType:#encode(person)] atIndex:0];
So, I try to extract in this way:
NSValue * value = [highscore objectAtIndex:0];
person p;
[value getValue:&p];
NSLog(#"%d", p.time);
The problem is that the final log doesn't show me 108000!
What is wrong?

Answer 1

Your code looks correct (and works for me), so I deduce that you aren't initializing highscore. So when you send the insertObject:atIndex: message to it, nothing happens. When you then send the objectAtIndex: method to it, you get nil back. When you send getValue: to the nil NSValue *value, it does nothing, so your person p is left filled with random stack garbage, which is why your NSLog doesn't print 108000.

Answer 2

As stated in my initial comment there rarely is a reason to do this kind of stuff with pure c structs. Instead go with real class objects:
If you're unfamiliar with the syntax below you may want to look at these quick tutorials on ObjC 2.0 as well as read Apple's documentation:
A Quick Objective-C 2.0 Tutorial
A Quick Objective-C 2.0 Tutorial: Part II
Person Class:
// "Person.h":
#interface Person : NSObject {}
#property (readwrite, strong, nonatomic) NSString *name;
#property (readwrite, assign, nonatomic) NSUInteger time;
#end
// "Person.m":
#implementation Person
#synthesize name = _name; // creates -(NSString *)name and -(void)setName:(NSString *)name
#synthesize time = _time; // creates -(NSUInteger)time and -(void)setTime:(NSUInteger)time
#end
Class use:
#import "Person.h"
//Store in highscore:
Person *person = [[Person alloc] init];
person.time = 108000; // equivalent to: [person setTime:108000];
person.name = #"Anonymous"; // equivalent to: [person setName:#"Anonymous"];
[highscore insertObject:person atIndex:0];
//Retreive from highscore:
Person *person = [highscore objectAtIndex:0]; // or in modern ObjC: highscore[0];
NSLog(#"%#: %lu", person.name, person.time);
// Result: "Anonymous: 108000"
To simplify debugging you may also want Person to implement the description method:
- (NSString *)description {
return [NSString stringWithFormat:#"<%# %p name:\"%#\" time:%lu>", [self class], self, self.name, self.time];
}
which will allow you to just do this for logging:
NSLog(#"%#", person);
// Result: "<Person 0x123456789 name:"Anonymous" time:108000>

Answer 3

Reimplement Person as an Objective-C object and reap the benefits:
Person.h:
#interface Person : NSObject
{
int _time;
NSString *_name;
}
#property (assign, nonatomic) int time;
#property (retain, nonatomic) NSString *name;
#end
Person.m:
#import "Person.h"
#interface Person
#synthesize time = _time;
#synthesize name = _name;
- (id)init
{
self = [super init];
if (self != nil)
{
// Add init here
}
return self;
}
- (void)dealloc
{
self.name = nil;
[super dealloc];
}
#end