Use Shared NSUserDefaults for XPC and Interface Builder Nibs

The default Interface Builder approach of using a "Shared User Defaults Controller" object breaks down if your app preferences are not stored in the standard place. Both my apps The Archive and the Word Counter for Mac are comprised of multiple executable applications. For The Archive, it's the main app and the Quick Entry popup window. They share some settings, like which theme and font size is used. To share these settings, I rely on NSUserDefault (or just UserDefaults in Swift now). I cannot use the UserDefaults.standard, though, because that is tied to the currently running app's bundle ID. In the case of the main app, it's the ID of the main app; but for the Quick Entry helper – or any helper app –, it's the helper's bundle ID. This way, the defaults dictionaries are not shared.

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Reusable View Components from Nibs

Just found this today in a Slack channel. It seems we can actually reference and re-use Xib files by overriding awakeFromCoder!

If we are loading from placeholder view, we create a real view and then we transfer some common properties from it and all it’s subviews, then we just return that instance in place of placeholder, otherwise we just return normal view (This method is implemented on NSObject so we can call super, but this still should be done with method swizzling instead of category smashing).

There's a sample project on GitHub. Let's tear it apart.

It works like this:

const int kNibReferencingTag = 616;

@implementation UIView (NibLoading)
// ...
- (id)awakeAfterUsingCoder:(NSCoder *)aDecoder
{
  if (self.tag == kNibReferencingTag) {
    //! placeholder
    UIView *realView = [[self class] loadInstanceFromNib];
    realView.frame = self.frame;
    realView.alpha = self.alpha;
    realView.backgroundColor = self.backgroundColor;
    realView.autoresizingMask = self.autoresizingMask;
    realView.autoresizesSubviews = self.autoresizesSubviews;

    for (UIView *view in self.subviews) {
      [realView addSubview:view];
    }
    return realView;
  }
  return [super awakeAfterUsingCoder:aDecoder];
}

When the kNibReferencingTag is set, the current instance (self) is treated as a prototype. From that prototype we transfer common properties to the realView which is properly loaded from a Nib. That means it doesn't go the kNibReferencingTag path but the usual path, deferring to super.

The sample app contains SomeView with its own Xib that should be reused.

In the app's Xib, we have a scene that uses it as follows:

<scenes>
    <!--View Controller-->
    <scene sceneID="4">
        <objects>
            <viewController id="2" customClass="ViewController" sceneMemberID="viewController">
                <view key="view" contentMode="scaleToFill" id="5">
                    <rect key="frame" x="0.0" y="20" width="768" height="1004"/>
                    <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                    <subviews>
                        <view tag="616" contentMode="scaleToFill" id="VTu-Cz-9kE" customClass="SomeView">
                            <rect key="frame" x="113" y="216" width="100" height="100"/>
                            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                            <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="calibratedWhite"/>
                        </view>
                        <view tag="616" contentMode="scaleToFill" id="7te-Q6-moz" customClass="SomeView">
                            <rect key="frame" x="199" y="446" width="100" height="100"/>
                            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                            <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="calibratedWhite"/>
                        </view>
                        <view tag="616" contentMode="scaleToFill" id="7vx-xh-xRD" customClass="SomeView">
                            <rect key="frame" x="375" y="231" width="100" height="100"/>
                            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                            <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="calibratedWhite"/>
                        </view>
                    </subviews>
                    <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="calibratedWhite"/>
                </view>
            </viewController>
            <placeholder placeholderIdentifier="IBFirstResponder" id="3" sceneMemberID="firstResponder"/>
        </objects>
    </scene>
</scenes>

I know, Xib files aren't the best to read. Here's what it boils down to:

  • Create a scene using a view controller of type ViewController.
  • In its main view place 3 subviews …
    • of type SomeView,
    • all with the tag 616,
    • and a few standard color properties – apparently all set to white. It doesn't matter anyway since the SomeView.xib will dictate what it really looks like.

Unlike @IBDesignable components, you won't have any live preview in Interface Builder. Just empty placeholder boxes.