Avoiding pointers

[subharb]

Hello guys,

In my code I need to create an object, then pass it to another object that will add it to a NSMutableArray that has as an attribute.
The thing is that the first object will be overwritten, and then added to the second's NSMutableArray.
And here comes the problem, the NSMutableArray instead of having 3 different objects it has 3 objects that are all the same. I believe it's because of the pointers, but is there a way that it doesnt point?

Thanks!

[smasher]

Post your code. It sounds like you're adding the same instance to the array three times; adding it to the array doesn't make a copy, so of course you get the same result three times.

//how to get three of the same object

MyClass *myObject = [[MyClass alloc] init]];

for(int i=0; i<3; i++){
     myObject.property = i;
     [myArray addObject:myObject];
}

[myObject release];

Now the array contains the same object three times, and "property" is set to "2" for that object.

It sounds like you want this:

//how to get three different objects

for(int i=0; i<3; i++){
     MyClass *myObject = [[MyClass alloc] init]];
     myObject.property = i;
     [myArray addObject:myObject];
     [myObject release];
}

Now you have three objects with three different properties.

EXTRA CREDIT: If you want the objects to be *nearly* identical with most of the properties the same you could write a copyWithZone method for the class, create one with the base properties set, and then [myObject copy] it before setting the different props and adding to the array. Just don't forget to release it; you own objects that are returned by a correctly written [ copy] method.

[subharb]

Great, the alloc solved it.
I supose since it gives another memory address it's virtually another object
So each position of the array points to one memory address with different values.

Thanks!

[smasher]

Alloc creates a new object and returns the address of the new object. Each object must have a different address; it is not possible for two objects to have the same address.

In your old code you had one object, but several pointers to it. The array has three pointers to the same object. Now you have multiple objects, which is what you need; the array points to three different memory addresses with three different objects.

[morrismountain]

Never leave the pointer uninitialized variables - things would not be so bad if uninitialized pointers always contain random values - the vast majority of random values are illegal pointer values, and get a program crash when they are used. The problem is that uninitialized variables tend to take the value of other, previously used pointer variables. These problems are very difficult to debug.