universal array in objective C - iphone

Question

I am making my first app, and already made it on android, and am now trying to make it on iphone, but have no objective c experience. The app is super simple except for one part, the array.
The app has a button, that when pressed, needs to store info into an array. The problem I am running into is that when I create the array in the method where the button-click actions take place, every time I click the button it creates a new array, defeating the point of the array. When I make the array outside of the method, it either doesn't pass into the method (error says undefined) or, when I declare the object in the .h file, the program compiles, but when I hit the button it crashes.
Any help would be greatly appreciated. Examples would be great, but even if someone could point me in the right direction of things to look up, that would save me from going bald.

Answer 1

Try something like this (this isn't ARC) -
#interface MyViewController : UIViewController {
NSMutableArray *myArray;
}
#implementation MyViewController
-(id)init {
self = [super init];
if (self) {
myArray = [[NSMutableArray alloc] init];
}
return self;
}
-(void)dealloc {
[myArray release];
[super dealloc];
}
-(IBAction)buttonPressed {
[myArray addObject:someObject];
}
#end

Answer 2

You need to declare your array as an instance variable (AKA "ivar") inside the curly braces section of the the interface declaration in your .h file, and also initialize it in your designated initializer.
In the .h file:
#interface MyClass : NSObject {
NSMutableArray *myArray
}
// methods
#end
In the .m file:
-(id)init {
self = [super init];
if (self) {
myArray = [NSMutableArray array];
}
return self;
}
Now you can use myArray in all instance methods of your class.
EDIT: This sample assumes that you are using automated reference counting. Since this is your first app, using ARC is a good idea (XCode asks you if you would like to use it when you create a new project).