addObject to NSArray - xcode

Question

I am a newbe and have been working all day readying/watching/searching for a solution to this. The following code works, but now how do I add an integer to the array?
//this works
NSArray *array = [NSArray arrayWithObjects:[NSNumber numberWithInt:10],
[NSNumber numberWithFloat:25.96], #"Hello World", nil];
for (id obj in array)
NSLog(#"%#", obj);
The following returns error: Use of undeclared identifier 'obj'
NSArray *array = [NSArray arrayWithObjects:[NSNumber numberWithInt:10],
[NSNumber numberWithFloat:25.96], #"Hello World", nil];
for (id obj in array)
[array addObject:7];
NSLog(#"%#", obj);

Answer 1

you must use a NSMutabbleArray not an NSArray to add objects dynamically and don't forget [] and arrayWithObjects is only for nsarray. try this:
NSMutableArray *array = [[NSMutableArray alloc] init];
[array addObject:[NSNumber numberWithInt:10]];
[array addObject:[NSNumber numberWithFloat:25.96]];
[array addObject:#"Hello World"];
[array addObject:[NSNumber numberWithInt:7]];
for (id obj in array) {
NSLog(#"%#", obj);
}
Just Copy paste this code and it will initiate the array with object you want and then show them.

Answer 2

There are several issues here:
You are attempting to mutate (change) an immutable array. You would need an NSMutableArray instead of NSArray to do what you want. (Incidentally, your actual NSArray creation code is fine.)
Your for() loop is blowing up mainly because you don't have braces to delimit your code. Absent braces, the compiler is going to use only the first line following the for as the loop contents. Hence your NSLog() is outside the loop, and obj out of scope.
I don't know why you don't have brackets around your addObject: line, as in [array addObject:...]. Did that even compile? Is that a copy and paste error?
Finally, you can't add a naked integer to a Cocoa collection such as NSArray. You would need to follow what you properly did earlier in your code: [array addObject:[NSNumber numberWithInt:7]].
Given that you were using indentation as syntax, I'm guessing maybe you have more of a Python (or similar) background? If so, you are going to have to quickly adjust some of your modes of thinking to program effectively in C or Objective-C. I urge you to get a beginners book on Cocoa programming and start at the beginning or you are going to get very frustrated very quickly.
Edit: I notice that after I posted you added brackets back in, so I struck #3 above. This leads to another important note: make sure that if you ask a question that you copy and paste the exact code that failed. Never re-type!

Answer 3

It's because your using indentation in your for loop which only considers the following line. Try this instead
    for (id obj in array) {
        [array addObject:[NSNumber numberWithInt:7]];
        NSLog(#"%#", obj);
}
Note
I think you need to use a NSMutableArray if you want to add objects after initialising it. Also it's not a good idea to modify a collection your looping through (in this case the loop will never end as you keep adding an object into an array your looping through). You can make a mutable version of the array by using this line.
NSMutableArray * mutArray = [NSMutableArray arrayWithArray:array];