How to load a UIView using a nib file created with

Question

I'm trying to do something a bit elaborate, but something that should be possible. So here is a challenge for all you experts out there (this forum is a pack of a lot of you guys :) ).

I'm creating a Questionnaire "component", which I want to load on a NavigationContoller (my QuestionManagerViewController). The "component" is an "empty" UIViewController, which can load different views depending on the question that needs to be answered.

The way I'm doing it is:

1. Create Question1View object as a UIView subclass, defining some IBOutlets.
2. Create (using Interface Builder) the Question1View.xib (HERE IS WHERE MY PROBLEM PROBABLY IS). I set both the UIViewController and the UIView to be of class Question1View.
3. I link the outlets with the view's component (using IB).

4. I override the initWithNib of my QuestionManagerViewController to look like this:

   - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
       if (self = [super initWithNibName:@"Question1View" bundle:nibBundleOrNil]) {
           // Custom initialization
       }
       return self;
   }
   

When I run the code, I'm getting this error:

2009-05-14 15:05:37.152 iMobiDines[17148:20b] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[UIViewController _loadViewFromNibNamed:bundle:] loaded the "Question1View" nib but the view outlet was not set.'

I'm sure there is a way to load the view using the nib file, without needing to create a viewController class.

Answer 1

Thank you all. I did find a way to do what I wanted.

1. Create your UIView with the IBOutlets you need.
2. Create the xib in IB, design it to you liking and link it like this: The File's Owner is of class UIViewController (No custom subclass, but the "real" one). The File Owner's view is connected to the main view and its class is declared as the one from step 1).
3. Connect your controls with the IBOutlets.

4. The DynamicViewController can run its logic to decide what view/xib to load. Once its made the decission, in the loadView method put something like this:

   NSArray* nibViews = [[NSBundle mainBundle] loadNibNamed:@"QPickOneView"
                                                     owner:self
                                                   options:nil];
   
   QPickOneView* myView = [ nibViews objectAtIndex: 1];
   
   myView.question = question;
   

That's it!

The main bundle's loadNibNamed method will take care of initializing the view and creating the connections.

Now the ViewController can display a view or another depending on the data in memory, and the "parent" screen doesn't need to bother with this logic.

Answer 2

For all those that need to manage more than one instance of the custom view, that is an Outlet Collection, I merged and customized the @Gonso, @AVeryDev and @Olie answers in this way:

1. Create a custom MyView : UIView and set it as "Custom Class" of the root UIView in the desired XIB;

2. Create all outlets you need in MyView (do it now because after point 3 the IB will propose you to connect outlets to the UIViewController and not to the custom view as we want);

3. Set your UIViewController as "File's Owner" of the custom view XIB;

4. In the UIViewController add a new UIViews for each instance of MyView you want, and connect them to UIViewController creating an Outlet Collection: these views will act as "wrapper" views for the custom view instances;

5. Finally, in the viewDidLoad of your UIViewController add the following lines:

NSArray *bundleObjects;
MyView *currView;
NSMutableArray *myViews = [NSMutableArray arrayWithCapacity:myWrapperViews.count];
for (UIView *currWrapperView in myWrapperViews) {
    bundleObjects = [[NSBundle mainBundle] loadNibNamed:@"MyView" owner:self options:nil];
    for (id object in bundleObjects) {
        if ([object isKindOfClass:[MyView class]]){
            currView = (MyView *)object;
            break;
        }
    }

    [currView.myLabel setText:@"myText"];
    [currView.myButton setTitle:@"myTitle" forState:UIControlStateNormal];
    //...

    [currWrapperView addSubview:currView];
    [myViews addObject:currView];
}
//self.myViews = myViews; if need to access them later..

Answer 3

This is a great question (+1) and the answers were almost helpful ;) Sorry guys, but I had a heck of a time slogging through this, though both Gonso & AVeryDev gave good hints. Hopefully, this answer will help others.

MyVC is the view controller holding all this stuff.

MySubview is the view that we want to load from a xib

• In MyVC.xib, create a view of type MySubView that is the right size & shape & positioned where you want it.

• In MyVC.h, have

  IBOutlet MySubview *mySubView
  // ...
  @property (nonatomic, retain) MySubview *mySubview;
  

• In MyVC.m, @synthesize mySubView; and don't forget to release it in dealloc.

• In MySubview.h, have an outlet/property for UIView *view (may be unnecessary, but worked for me.) Synthesize & release it in .m
• In MySubview.xib
  • set file owner type to MySubview, and link the view property to your view.
  • Lay out all the bits & connect to the IBOutlet's as desired

• Back in MyVC.m, have

  NSArray *xibviews = [[NSBundle mainBundle] loadNibNamed: @"MySubview" owner: mySubview options: NULL];
  MySubview *msView = [xibviews objectAtIndex: 0];
  msView.frame = mySubview.frame;
  UIView *oldView = mySubview;
  // Too simple: [self.view insertSubview: msView aboveSubview: mySubview];
  [[mySubview superview] insertSubview: msView aboveSubview: mySubview]; // allows nesting
  self.mySubview = msView;
  [oldCBView removeFromSuperview];
  

The tricky bit for me was: the hints in the other answers loaded my view from the xib, but did NOT replace the view in MyVC (duh!) -- I had to swap that out on my own.

Also, to get access to mySubview's methods, the view property in the .xib file must be set to MySubview. Otherwise, it comes back as a plain-old UIView.

If there's a way to load mySubview directly from its own xib, that'd rock, but this got me where I needed to be.

Answer 4

I have a convention of naming xibs with views in them the same as the view. Same as one would do for a view controller. Then, I don't have to write out class names in code. I load a UIView from a nib file with the same name.

Example for a class called MyView.

• Create a nib file called MyView.xib in Interface Builder
• In Interface Builder, add a UIView. Set its class to MyView. Customize to your heart's content, wire up instance variables of MyView to subviews you might want to access later.

• In your code, create a new MyView like this:

  MyView *myView = [MyView nib_viewFromNibWithOwner:owner];

Here's the category for this:

@implementation UIView (nib)

+ (id) nib_viewFromNib {
    return [self nib_viewFromNibWithOwner:nil];
}

+ (id) nib_viewFromNibWithOwner:(id)owner {
    NSString *className = NSStringFromClass([self class]);
    NSArray *nib = [[NSBundle mainBundle] loadNibNamed:className owner:owner options:nil];
    UIView *view = nil;
    for(UIView *v in nib) {
        if ([v isKindOfClass:[self class]]) {
            view = v;
            break;
        }
    }
    assert(view != nil && "View for class not found in nib file");
    [view nib_viewDidLoad];
    return view;
}

// override this to do custom setup
-(void)nib_viewDidLoad {

}

I'd then wire up buttons with actions from the controller I am using, and set things on labels using the outlets in my custom view subclass.

Answer 5

I would use UINib to instantiate a custom UIView to be reused

UINib *customNib = [UINib nibWithNibName:@"MyCustomView" bundle:nil];
MyCustomViewClass *customView = [[customNib instantiateWithOwner:self options:nil] objectAtIndex:0];
[self.view addSubview:customView];

Files needed in this case are MyCustomView.xib, MyCustomViewClass.h and MyCustomViewClass.m Note that [UINib instantiateWithOwner] returns an array, so you should use the element which reflects the UIView you want to re-use. In this case it's the first element.

Answer 6

I'm not sure what some of the answers are talking about, but I need to put this answer here for when I search in Google next time. Keywords: "How to load a UIView from a nib" or "How to load a UIView from an NSBundle."

Here's the code almost 100% straight up from the Apress Beginning iPhone 3 book (page 247, "Using The New Table View Cell"):

- (void)viewDidLoad {
    [super viewDidLoad];
    NSArray *bundle = [[NSBundle mainBundle] loadNibNamed:@"Blah"
                                                 owner:self options:nil];
    Blah *blah;
    for (id object in bundle) {
        if ([object isKindOfClass:[Blah class]]) {
            blah = (Blah *)object;
            break;
        }
    }   
    assert(blah != nil && "blah can't be nil");
    [self.view addSubview: blah];
} 

This supposes you have a UIView subclass called Blah, a nib called Blah which contains a UIView which has its class set to Blah.

---

Category: NSObject+LoadFromNib

#import "NSObject+LoadFromNib.h"

@implementation NSObject (LoadFromNib)

+ (id)loadFromNib:(NSString *)name classToLoad:(Class)classToLoad {
    NSArray *bundle = [[NSBundle mainBundle] loadNibNamed:name owner:self options:nil];
    for (id object in bundle) {
        if ([object isKindOfClass:classToLoad]) {
            return object;
        }
    }
    return nil;
}

@end

---

Swift Extension

extension UIView {
    class func loadFromNib<T>(withName nibName: String) -> T? {
        let nib  = UINib.init(nibName: nibName, bundle: nil)
        let nibObjects = nib.instantiate(withOwner: nil, options: nil)
        for object in nibObjects {
            if let result = object as? T {
                return result
            }
        }
        return nil
    }
}

And an example in use:

class SomeView: UIView {
    class func loadFromNib() -> SomeView? {
        return self.loadFromNib(withName: "SomeView")
    }
}