IBOutletCollection set ordering in Interface Builder - objective-c

Question

I am using IBOutletCollections to group several Instances of similar UI Elements. In particular I group a number of UIButtons (which are similar to buzzers in a quiz game) and a group of UILabels (which display the score). I want to make sure that the label directly over the button updates the score. I figured that it is easiest to access them by index. Unfortunately even if I add them in the same order, they do not always have the same indexes. Is there a way in Interface Builder to set the correct ordering.

Answer 1

EDIT: Several commenters have claimed that more recent versions of Xcode return IBOutletCollections in the order the connections are made. Others have claimed that this approach didn't work for them in storyboards. I haven't tested this myself, but if you're willing to rely on undocumented behavior, then you may find that the explicit sorting I've proposed below is no longer necessary.
Unfortunately there doesn't seem to be any way to control the order of an IBOutletCollection in IB, so you'll need to sort the array after it's been loaded based on some property of the views. You could sort the views based on their tag property, but manually setting tags in IB can be rather tedious.
Fortunately we tend to lay out our views in the order we want to access them, so it's often sufficient to sort the array based on x or y position like this:
- (void)viewDidLoad
{
[super viewDidLoad];
// Order the labels based on their y position
self.labelsArray = [self.labelsArray sortedArrayUsingComparator:^NSComparisonResult(UILabel *label1, UILabel *label2) {
CGFloat label1Top = CGRectGetMinY(label1.frame);
CGFloat label2Top = CGRectGetMinY(label2.frame);
return [#(label1Top) compare:#(label2Top)];
}];
}

Answer 2

I ran with cduhn's answer and made this NSArray category.
If now xcode really preserves the design-time order this code is not really needed, but if you find yourself having to create/recreate large collections in IB and don't want to worry about messing up this could help (at run time). Also a note: most likely the order in which the objects were added to the collection had something to do with the "Object ID" you find in the Identity Inspector tab, which can get sporadic as you edit the interface and introduce new objects to the collection at a later time.
.h
#interface NSArray (sortBy)
- (NSArray*) sortByObjectTag;
- (NSArray*) sortByUIViewOriginX;
- (NSArray*) sortByUIViewOriginY;
#end
.m
#implementation NSArray (sortBy)
- (NSArray*) sortByObjectTag
{
return [self sortedArrayUsingComparator:^NSComparisonResult(id objA, id objB){
return(
([objA tag] < [objB tag]) ? NSOrderedAscending :
([objA tag] > [objB tag]) ? NSOrderedDescending :
NSOrderedSame);
}];
}
- (NSArray*) sortByUIViewOriginX
{
return [self sortedArrayUsingComparator:^NSComparisonResult(id objA, id objB){
return(
([objA frame].origin.x < [objB frame].origin.x) ? NSOrderedAscending :
([objA frame].origin.x > [objB frame].origin.x) ? NSOrderedDescending :
NSOrderedSame);
}];
}
- (NSArray*) sortByUIViewOriginY
{
return [self sortedArrayUsingComparator:^NSComparisonResult(id objA, id objB){
return(
([objA frame].origin.y < [objB frame].origin.y) ? NSOrderedAscending :
([objA frame].origin.y > [objB frame].origin.y) ? NSOrderedDescending :
NSOrderedSame);
}];
}
#end
Then include the header file as you chose to name it and the code can be:
- (void)viewDidLoad
{
[super viewDidLoad];
// Order the labels based on their y position
self.labelsArray = [self.labelsArray sortByUIViewOriginY];
}

Answer 3

Not sure when this changed exactly, but as of Xcode 4.2 at least, this no longer seems to be a problem. IBOutletCollections now preserve the order in which the views were added in Interface Builder.
UPDATE:
I made a test project to verify that this is the case: IBOutletCollectionTest

Answer 4

Not as far as I am aware.
As a workaround, you could assign each of them a tag, sequentially. Have the buttons range 100, 101, 102, etc. and the labels 200, 201, 202, etc. Then add 100 to the button's tag to get its corresponding label's tag. You can then get the label by using viewForTag:.
Alternatively, you could group the corresponding objects into their own UIView, so you only have one button and one label per view.

Answer 5

I found that Xcode sorts the collection alphabetically using the ID of the connection.
If you open the version editor on your nib file you can easily edit the id's (making sure they are unique otherwise Xcode will crash).
<outletCollection property="characterKeys" destination="QFa-Hp-9dk" id="aaa-0g-pwu"/>
<outletCollection property="characterKeys" destination="ahU-9i-wYh" id="aab-EL-hVT"/>
<outletCollection property="characterKeys" destination="Kkl-0x-mFt" id="aac-0c-Ot1"/>
<outletCollection property="characterKeys" destination="Neo-PS-Fel" id="aad-bK-O6z"/>
<outletCollection property="characterKeys" destination="AYG-dm-klF" id="aae-Qq-bam"/>
<outletCollection property="characterKeys" destination="Blz-fZ-cMU" id="aaf-lU-g7V"/>
<outletCollection property="characterKeys" destination="JCi-Hs-8Cx" id="aag-zq-6hK"/>
<outletCollection property="characterKeys" destination="DzW-qz-gFo" id="aah-yJ-wbx"/>
It helps if you first order your object manually in the Document Outline of IB so they show up in sequence in the the xml code.

Answer 6

The extension proposed by #scott-gardner is great & solves problems such as a collection of [UIButtons] not showing in the expected order. The below code is simply updated for Swift 5. Thanks really goes to Scott for this!
extension Array where Element: UIView {
/**
Sorts an array of `UIView`s or subclasses by `tag`. For example, this is useful when working with `IBOutletCollection`s, whose order of elements can be changed when manipulating the view objects in Interface Builder. Just tag your views in Interface Builder and then call this method on your `IBOutletCollection`s in `viewDidLoad()`.
- author: Scott Gardner
- seealso:
* [Source on GitHub](bit dot ly/SortUIViewsInPlaceByTag)
*/
mutating func sortUIViewsInPlaceByTag() {
sort { (left: Element, right: Element) in
left.tag < right.tag
}
}
}

Answer 7

It seems very random how IBOutletCollection is ordered. Maybe I am not understanding Nick Lockwood's methodology correctly - but I as well made a new project, added a bunch of UILabels, and connected them to a collection in the order they were added to the view.
After logging, I got a random order. It was very frustrating.
My workaround was setting tags in IB and then sorting the collections like so:
[self setResultRow1:[self sortCollection: [self resultRow1]]];
Here, resultRow1 is an IBOutletCollection of about 7 labels, with tags set through IB. Here is the sort method:
-(NSArray *)sortCollection:(NSArray *)toSort {
NSArray *sortedArray;
sortedArray = [toSort sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
NSNumber *tag1 = [NSNumber numberWithInt:[(UILabel*)a tag]];
NSNumber *tag2 = [NSNumber numberWithInt:[(UILabel*)b tag]];
return [tag1 compare:tag2];
}];
return sortedArray;
}
Doing this, I can now access objects by using [resultRow1 objectAtIndex: i] or such. This saves overhead of having to iterate through and compare tags every time I need to access an element.

Answer 8

I needed this ordering for a collection of UITextField objects for setting where the "Next" button on the keyboard would lead to (field tabbing). This is going to be an international app so I wanted the language direction to be ambiguous.
.h
#import <Foundation/Foundation.h>
#interface NSArray (UIViewSort)
- (NSArray *)sortByUIViewOrigin;
#end
.m
#import "NSArray+UIViewSort.h"
#implementation NSArray (UIViewSort)
- (NSArray *)sortByUIViewOrigin {
NSLocaleLanguageDirection horizontalDirection = [NSLocale characterDirectionForLanguage:[[NSLocale currentLocale] objectForKey:NSLocaleLanguageCode]];
NSLocaleLanguageDirection verticalDirection = [NSLocale lineDirectionForLanguage:[[NSLocale currentLocale] objectForKey:NSLocaleLanguageCode]];
UIView *window = [[UIApplication sharedApplication] delegate].window;
return [self sortedArrayUsingComparator:^NSComparisonResult(id object1, id object2) {
CGPoint viewOrigin1 = [(UIView *)object1 convertPoint:((UIView *)object1).frame.origin toView:window];
CGPoint viewOrigin2 = [(UIView *)object2 convertPoint:((UIView *)object2).frame.origin toView:window];
if (viewOrigin1.y < viewOrigin2.y) {
return (verticalDirection == kCFLocaleLanguageDirectionLeftToRight) ? NSOrderedDescending : NSOrderedAscending;
}
else if (viewOrigin1.y > viewOrigin2.y) {
return (verticalDirection == kCFLocaleLanguageDirectionLeftToRight) ? NSOrderedAscending : NSOrderedDescending;
}
else if (viewOrigin1.x < viewOrigin2.x) {
return (horizontalDirection == kCFLocaleLanguageDirectionTopToBottom) ? NSOrderedDescending : NSOrderedAscending;
}
else if (viewOrigin1.x > viewOrigin2.x) {
return (horizontalDirection == kCFLocaleLanguageDirectionTopToBottom) ? NSOrderedAscending : NSOrderedDescending;
}
else return NSOrderedSame;
}];
}
#end
Usage (after layout)
- (void)viewDidAppear:(BOOL)animated {
_availableTextFields = [_availableTextFields sortByUIViewOrigin];
UITextField *previousField;
for (UITextField *field in _availableTextFields) {
if (previousField) {
previousField.nextTextField = field;
}
previousField = field;
}
}

Answer 9

Here's an extension I created on Array<UIView> to sort by tag, e.g., useful when working w/ IBOutletCollections.
extension Array where Element: UIView {
/**
Sorts an array of `UIView`s or subclasses by `tag`. For example, this is useful when working with `IBOutletCollection`s, whose order of elements can be changed when manipulating the view objects in Interface Builder. Just tag your views in Interface Builder and then call this method on your `IBOutletCollection`s in `viewDidLoad()`.
- author: Scott Gardner
- seealso:
* [Source on GitHub](http://bit.ly/SortUIViewsInPlaceByTag)
*/
mutating func sortUIViewsInPlaceByTag() {
sortInPlace { (left: Element, right: Element) in
left.tag < right.tag
}
}
}

Answer 10

I used the extension proposed by #scott-gardner to order Image Views in order to display counters using individual png images of dot-matrix digits.
It worked like a charm in Swift 5.
self.dayDigits.sortUIViewsInPlaceByTag()
func updateDayDigits(countString: String){
for i in 0...4 {
dayDigits[i].image = offDigitImage
}
let length = countString.count - 1
for i in 0...length {
let char = Array(countString)[length-i]
dayDigits[i].image = digitImages[char.wholeNumberValue!]
}
}