Store References to Variable in NSMutableArray

Question

Hi Everyone:

I am looking for a way to store references to variables inside a NSMutableArray. As variables are going to be created dynamically based upon what the user has chosen, I want to be able to simply sort through this array and get references to these created variables. In case it matters, I am creating a iPhone project. However, when I attempt to do this using the following code:

for (int a = 0; a < 10; a++)
{
UIView *tempView;
[listingOfViews addObject:tempView];
}

for (int a = 0; a < [listingOfViews count]; a++)
{
[listingOfViews objectAtIndex:a] = defaultViewStructure;
}

It gives me this error: "error: lvalue required as left operand of assignment"

Any ideas?

EDIT: Also, I get this error: "error: request for member 'size' in something not a structure or union"

When I attempt to do

for (int a = 0; a < [listingOfViews count]; a++)
{
[listingOfViews objectAtIndex:a].size.height = ...
}

Answer 1

What you mean is:

[listingOfViews replaceObjectAtIndex:a withObject:defaultViewStructure];

But it'll crash when you try to put those uninitialized tempView pointers into the array. What are you really trying to do here? I think it may be time to step back and start with the basics of Objective-C. It looks like you're trying to port C++ concepts directly into ObjC, and they do things very differently.

You may want to start with Programming in Objective-C, and then probably Cocoa Programming for Mac OS X. (The latter is Mac-based, rather than iPhone, but it's still the best starting point.)

Answer 2

To your second question:

for (int a = 0; a < [listingOfViews count]; a++)
{
    [listingOfViews objectAtIndex:a].size.height = ...
}

There's a misunderstanding here (a UIView does not have a -size, it has a -frame that includes a size), coupled with something that is actually a little tricky because of the very confusing dot notation they added in Obj-C 2 and an unfortunate breakdown of the object model when you get to structs. The way you do what you're trying to do is:

UIView *view = [listingOfViews objectAtIndex:a];
NSRect frame = [view frame];
frame.size.height = ...
[view setFrame:frame];

There are ways to condense the number of lines slightly, but you do need to fetch an NSRect struct, modify it, and then set it back. You can't modify the height in one call on most views.