iOS (Re)Use a NIB as a Template - objective-c

Question

I have created a nib file with different views. I was planning to use this nib file as a template, much like in web (i.e. html). So create a new instance of this nib fill it with actual data, create another new instance of nib & fill with actual data etc...
But when I try to do this, nib instance is not behaving the same. Only one gets created. Am I missing something? Aren't nib files supposed to be used this way?
Here's how I tried to use my nib file -
int yCoord = 0;
for(int i=0; i<[resultSet count]; i++)
{
[[NSBundle mainBundle] loadNibNamed:#"msgView" owner:self options:nil];
UIView *tmpMsgView = [[UIView alloc] initWithFrame:CGRectMake(0, yCoord, msgView.view.frame.size.width, msgView.view.frame.size.height)];
tmpMsgView = msgView.view;
UILabel *senderLabel = (UILabel *)[tmpMsgView viewWithTag:1];
[senderLabel setText:#"trial"];
[self.view addSubview:tmpMsgView];
[tmpMsgView release];
yCoord += msg.view.frame.size.height;
}
this msgView is hooked up to the nib file (through IB) and the owner of that nib file too is defined as this viewController class.

Answer 1

Your code is adding the same instance over and over again, not a new instance each time.
UIView *testView = [[UIView alloc] init];
testView.backgroundColor = [UIColor blueColor];
for (int i=0; i<5; i++) {
testView.frame = CGRectMake(0.0, (i+1)*40.0, 200.0, 20.0);
[self.window addSubview:testView];
}
[testView release];
and
for (int i=0; i<5; i++) {
UIView *testView = [[UIView alloc] init];
testView.backgroundColor = [UIColor blueColor];
testView.frame = CGRectMake(0.0, (i+1)*40.0, 200.0, 20.0);
[self.window addSubview:testView];
[testView release];
}
are two very different things.
the first actually makes very little sense and results in a single blue bar,
the second makes much more sense and results in 5 blue bars -- I think this is what you want.
look at the following, it will create 5 rectangles with all different colors -- this is to illustrate that each is rectangle is its seperate instance loaded from a nib:
for (int i=0; i<5; i++) {
NSArray *nibObjects = [[NSBundle mainBundle] loadNibNamed:#"aView" owner:self options:nil];
UIView *nibView = [nibObjects objectAtIndex:0];
nibView.backgroundColor = [UIColor colorWithRed:(i+1)*0.14 green:(i+1)*0.11 blue:200.0 alpha:1.0];
nibView.frame = CGRectMake(0.0, (i+1)*40.0, 200.0, 20.0);
[self.window addSubview:nibView];
}
now, if we assign our nibObjects array only once before the loop, we again have the same issue in that we add the same instance over and over again, which will result in one rectangle only:
NSArray *nibObjects = [[NSBundle mainBundle] loadNibNamed:#"aView" owner:self options:nil];
for (int i=0; i<5; i++) {
UIView *nibView = [nibObjects objectAtIndex:0];
nibView.backgroundColor = [UIColor colorWithRed:(i+1)*0.14 green:(i+1)*0.11 blue:200.0 alpha:1.0];
nibView.frame = CGRectMake(0.0, (i+1)*40.0, 200.0, 20.0);
[self.window addSubview:nibView];
}
hope this helps

Answer 2

You have memory management issues in your code.
UIView *tmpMsgView = [[UIView alloc] initWithFrame:CGRectMake(0, yCoord, msgView.view.frame.size.width, msgView.view.frame.size.height)];
You alloc/init a UIView and on the next line you store some other view in the variable. You lose the pointer to the UIView and therefore you leak its memory.
Whether the code using senderLabel will work depends on what you defined in the nib file.
In [tmpMsgView release]; you're most probably releasing something you do not own (the pointer no longer points to the UIView you alloc/inited). The issue here depends on how you declare msgView. If you are releasing an object you do not own, it might get deallocated and that might be the reason you do not see it in your app.

Answer 3

What you are trying to do is fine - this is what is routinely done for loading table view cells, for example.
If I do this I have a single outlet from the view controller (which is set as files owner which you have done). This will be the topmost object in the nib, eg a UIView. All of your other Nib components are just subviews of this, you can identify with tags or, if your topmost view is a custom view, that can have outlets which are connected appropriately.
When you do loadNibNamed this will set your outlet ivar to the topmost object. You then assign this to a method level variable, and set your ivar back to nil. You can then do what you like with this before adding it as a subview to something else. Next time you load the nib, you get another fresh version.
Hope that makes sense, let me know if I can add anything else. The problem in your code is that you are doing things with msgView.view instead of the top level object.