Xcode 12 fails to interpret traitCollection with Interface builder

Number:rdar://FB8799442 Date Originated:14-Oct-2020 11:44 AM
Status:Duplicate/23549463 Resolved:
Product:Xcode Product Version:Version 12.0.1 (12A7300)
Classification:Incorrect/Unexpected Behavior Reproducible:Always
This is a duplicate of radar #23549463

When using IBDesignable properties, as a workaround for not having sizing class support, a common approach is to use traitCollection with IBDesignable variables one per sizing class. However Xcode doesn’t interpret traitCollection and always uses any / any when showing interface builder.. This works as expected in the similar and device, however in interface builder only any / any is used.

Steps to Reproduce:
Setup IBInspectable variables for each sizing class :-
@property (nonatomic) IBInspectable CGFloat AaShadowHeight;
@property (nonatomic) IBInspectable CGFloat RrShadowHeight;
@property (nonatomic) IBInspectable CGFloat CcShadowHeight;
@property (nonatomic) IBInspectable CGFloat RcShadowHeight;

Use those variables in your drawRect method.
Set a different value for each property.

Use self.traitCollection in your drawRect method :-

- (void)drawRect:(CGRect)rect {
    // Drawing code
    CGFloat l_shadHeight = self.AaShadHeight; // 24.1
    if (self.traitCollection.horizontalSizeClass == UIUserInterfaceSizeClassCompact)
        if (self.traitCollection.verticalSizeClass == UIUserInterfaceSizeClassCompact)
            //iphone3.5 / 4 / 4.7 landscape
            l_shadHeight = self.CcShadHeight;
    if (self.traitCollection.horizontalSizeClass == UIUserInterfaceSizeClassRegular)
        if (self.traitCollection.verticalSizeClass == UIUserInterfaceSizeClassRegular)
            //ipad landscape
            l_shadHeight = self.RrShadHeight;
        if (self.traitCollection.verticalSizeClass == UIUserInterfaceSizeClassCompact)
            l_shadHeight = self.RcShadHeight;

Build your framework file (contains drawing class).
Open your storyboard.
Change your sizing class to regular / regular.
Change the IBDesignable value for regular / regular - see no change.
Change the IBDesignable value for any / any see the change.

Expected Results:
To have traitCollection work with the interface builder when using IBDesignable properties for each sizing class.

Actual Results:
Any / any IBDesignable property is used in all cases




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