Ytukyg

While trying to setup email subject and content via UIActivityViewController I worked with the .setValue func in Swift. The key to set the subject was easy to find, but I couldn't find the key to set the content.

activityViewController.setValue("Subject", forKey: "Subject")



//Key "Content" is not defined

activityViewController.setValue("Content", forKey: "Content"

In this context I searched for a "list" with all possible keys, but I couldn't find anything (Even in the API doc from Apple https://developer.apple.com/documentation/objectivec/nsobject/1415969-setvalue). So I would like to ask in general where to find such a list, independent of this particular case.

You're accessing private internal details of UIActivityViewController. There is no telling what that ivar is used for and under what conditions is it safe to set it. setValue(_:forKey:) is a dynamic method that will let you access arbitrary internals, but that doesn't mean you should.

For exploratory purposes, you can use tools like class-dump or Hopper to reverse engineer the class, or you can query it at runtime like this:

let cls = UIActivityViewController.self



var count: UInt32 = 0

let ivars = class_copyIvarList(cls, &count)!

for i in 0..<count {

    let ivar = ivars[Int(i)]

    let name = ivar_getName(ivar)!

    print(String(cString: name))

}



print("---")



let properties = class_copyPropertyList(cls, &count)!

for i in 0..<count {

    let property = properties[Int(i)]

    let name = property_getName(property)

    print(String(cString: name))

}

That will print a list of all the ivars and properties, which are most of what setValue(_:forKey:) can access by default on the current class. It won't include properties from the superclass or non-property accessors. You'd have to deeper for that. (But again, this isn't how setValue(_:forKey:) is used. You use it by reading the documentation for the class, not just poking around.

Using class-dump, you'd see the following for UIActivityViewController:

class-dump -C '^UIActivityViewController$' /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/Library/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore



///// ... HEADER OMITTED ....



//

// File: /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/Library/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore

// UUID: 2DB941E0-513E-3750-9278-C8AFB85CB3C0

//

//                           Arch: x86_64

//                Current version: 61000.0.0

//          Compatibility version: 1.0.0

//                 Source version: 3698.29.8.0.0

//

// Objective-C Garbage Collection: Unsupported

//



@interface UIActivityViewController : UIViewController <UIAlertControllerContaining, UIAlertControllerVisualStyleProviding, UIViewControllerRestoration, UIActionSheetPresentationControllerDelegate, _UIActivityHelperDelegate, _UIShareExtensionHost>

{

    _Bool _waitingForInitialShareServicePreferredContentSize;

    _Bool _shareServicePreferredContentSizeIsValid;

    _Bool __viewServiceBeganConnecting;

    _Bool _dismissalDetectionOfViewControllerForSelectedActivityShouldAutoCancel;

    _Bool _willDismissActivityViewController;

    _Bool _performActivityForStateRestoration;

    _Bool _shouldMatchOnlyUserElectedExtensions;

    _Bool _hasPerformedInitialPresentation;

    _Bool _isPerformingPresentation;

    _Bool _allowsEmbedding;

    _Bool _showKeyboardAutomatically;

    _Bool _sourceIsManaged;

    CDUnknownBlockType _completionHandler;

    CDUnknownBlockType _completionWithItemsHandler;

    NSArray *_excludedActivityTypes;

    _UIShareExtensionRemoteViewController *_remoteContentViewController;

    NSExtension *_shareExtension;

    id <NSCopying> _extensionRequestIdentifier;

    id <_UIShareExtensionService> _shareExtensionService;

    UISUIActivityViewControllerConfiguration *_activityViewControllerConfiguration;

    _UIActivityGroupListViewController *_placeholderViewController;

    NSArray *_activityItems;

    NSArray *_applicationActivities;

    NSMutableDictionary *_activitiesByUUID;

    _UIActivityHelper *_activityHelper;

    long long _originalPopoverBackgroundStyle;

    Class _originalPopoverBackgroundViewClass;

    CDUnknownBlockType __popoverDismissalAction;

    CDUnknownBlockType _activityPresentationCompletionHandler;

    UIAlertController *_activityAlertController;

    _UIAlertControllerShimPresenter *_activityAlertControllerShimPresenter;

    UIAlertAction *_activityAlertCancelAction;

    NSArray *_activityItemProviderOperations;

    NSOperationQueue *_activityItemProviderOperationQueue;

    long long _totalProviderCount;

    long long _completedProviderCount;

    unsigned long long _backgroundTaskIdentifier;

    NSString *_subject;

    unsigned long long _clientAttemptedInitialPresentationOrEmbeddingTimestamp;

    unsigned long long _beginPerformingActivityTimestamp;

    unsigned long long _viewWillAppearTimestamp;

    unsigned long long _readyToInteractTimestamp;

    NSArray *_activityTypesToCreateInShareService;

    NSArray *_resolvedActivityItemsForCurrentActivity;

    CDUnknownBlockType _shareSheetReadyToInteractHandler;

    CDUnknownBlockType _preCompletionHandler;

    NSArray *_includedActivityTypes;

    long long _excludedActivityCategories;

    NSArray *_activityTypeOrder;

    UIActivity *_activity;

    UIViewController *_activityViewController;

    id <UIActivityViewControllerDelegate> _airDropDelegate;

}



+ (id)viewControllerWithRestorationIdentifierPath:(id)arg1 coder:(id)arg2;

+ (double)_asyncPresentationTimeout;

+ (_Bool)_popoverPresentationUsesModernPresentation;

+ (_Bool)_usesActionSheetPresentationController;

@property(nonatomic) __weak id <UIActivityViewControllerDelegate> airDropDelegate; // @synthesize airDropDelegate=_airDropDelegate;

@property(retain, nonatomic) UIViewController *activityViewController; // @synthesize activityViewController=_activityViewController;

@property(retain, nonatomic) UIActivity *activity; // @synthesize activity=_activity;

@property(nonatomic) _Bool sourceIsManaged; // @synthesize sourceIsManaged=_sourceIsManaged;

@property(nonatomic) _Bool showKeyboardAutomatically; // @synthesize showKeyboardAutomatically=_showKeyboardAutomatically;

@property(nonatomic) _Bool allowsEmbedding; // @synthesize allowsEmbedding=_allowsEmbedding;

@property(copy, nonatomic) NSArray *activityTypeOrder; // @synthesize activityTypeOrder=_activityTypeOrder;

@property(nonatomic) long long excludedActivityCategories; // @synthesize excludedActivityCategories=_excludedActivityCategories;

@property(copy, nonatomic) NSArray *includedActivityTypes; // @synthesize includedActivityTypes=_includedActivityTypes;

@property(copy, nonatomic) CDUnknownBlockType preCompletionHandler; // @synthesize preCompletionHandler=_preCompletionHandler;

@property(copy, nonatomic, getter=_shareSheetReadyToInteractHandler, setter=_setShareSheetReadyToInteractHandler:) CDUnknownBlockType shareSheetReadyToInteractHandler; // @synthesize shareSheetReadyToInteractHandler=_shareSheetReadyToInteractHandler;

@property(readonly, nonatomic) NSArray *resolvedActivityItemsForCurrentActivity; // @synthesize resolvedActivityItemsForCurrentActivity=_resolvedActivityItemsForCurrentActivity;

@property(retain, nonatomic) NSArray *activityTypesToCreateInShareService; // @synthesize activityTypesToCreateInShareService=_activityTypesToCreateInShareService;

@property(nonatomic, getter=_readyToInteractTimestamp, setter=_setReadyToInteractTimestamp:) unsigned long long readyToInteractTimestamp; // @synthesize readyToInteractTimestamp=_readyToInteractTimestamp;

@property(nonatomic, getter=_viewWillAppearTimestamp, setter=_setViewWillAppearTimestamp:) unsigned long long viewWillAppearTimestamp; // @synthesize viewWillAppearTimestamp=_viewWillAppearTimestamp;

@property(nonatomic, getter=_beginPerformingActivityTimestamp, setter=_setBeginPerformingActivityTimestamp:) unsigned long long beginPerformingActivityTimestamp; // @synthesize beginPerformingActivityTimestamp=_beginPerformingActivityTimestamp;

@property(nonatomic, getter=_clientAttemptedInitialPresentationOrEmbeddingTimestamp, setter=_setClientAttemptedInitialPresentationOrEmbeddingTimestamp:) unsigned long long clientAttemptedInitialPresentationOrEmbeddingTimestamp; // @synthesize clientAttemptedInitialPresentationOrEmbeddingTimestamp=_clientAttemptedInitialPresentationOrEmbeddingTimestamp;

@property(nonatomic, getter=_isPerformingPresentation, setter=_setIsPerformingPresentation:) _Bool isPerformingPresentation; // @synthesize isPerformingPresentation=_isPerformingPresentation;

@property(nonatomic, getter=_hasPerformedInitialPresentation, setter=_setHasPerformedInitialPresentation:) _Bool hasPerformedInitialPresentation; // @synthesize hasPerformedInitialPresentation=_hasPerformedInitialPresentation;

@property(nonatomic) _Bool shouldMatchOnlyUserElectedExtensions; // @synthesize shouldMatchOnlyUserElectedExtensions=_shouldMatchOnlyUserElectedExtensions;

@property(nonatomic) _Bool performActivityForStateRestoration; // @synthesize performActivityForStateRestoration=_performActivityForStateRestoration;

@property(copy, nonatomic) NSString *subject; // @synthesize subject=_subject;

@property(nonatomic) unsigned long long backgroundTaskIdentifier; // @synthesize backgroundTaskIdentifier=_backgroundTaskIdentifier;

@property(nonatomic) long long completedProviderCount; // @synthesize completedProviderCount=_completedProviderCount;

@property(nonatomic) long long totalProviderCount; // @synthesize totalProviderCount=_totalProviderCount;

@property(retain, nonatomic) NSOperationQueue *activityItemProviderOperationQueue; // @synthesize activityItemProviderOperationQueue=_activityItemProviderOperationQueue;

@property(retain, nonatomic) NSArray *activityItemProviderOperations; // @synthesize activityItemProviderOperations=_activityItemProviderOperations;

@property(retain, nonatomic) UIAlertAction *activityAlertCancelAction; // @synthesize activityAlertCancelAction=_activityAlertCancelAction;

@property(retain, nonatomic) _UIAlertControllerShimPresenter *activityAlertControllerShimPresenter; // @synthesize activityAlertControllerShimPresenter=_activityAlertControllerShimPresenter;

@property(retain, nonatomic) UIAlertController *activityAlertController; // @synthesize activityAlertController=_activityAlertController;

@property(copy, nonatomic, getter=_activityPresentationCompletionHandler, setter=_setActivityPresentationCompletionHandler:) CDUnknownBlockType activityPresentationCompletionHandler; // @synthesize activityPresentationCompletionHandler=_activityPresentationCompletionHandler;

@property(nonatomic) _Bool willDismissActivityViewController; // @synthesize willDismissActivityViewController=_willDismissActivityViewController;

@property(nonatomic) _Bool dismissalDetectionOfViewControllerForSelectedActivityShouldAutoCancel; // @synthesize dismissalDetectionOfViewControllerForSelectedActivityShouldAutoCancel=_dismissalDetectionOfViewControllerForSelectedActivityShouldAutoCancel;

@property(copy, nonatomic) CDUnknownBlockType _popoverDismissalAction; // @synthesize _popoverDismissalAction=__popoverDismissalAction;

@property(retain, nonatomic) Class originalPopoverBackgroundViewClass; // @synthesize originalPopoverBackgroundViewClass=_originalPopoverBackgroundViewClass;

@property(nonatomic) long long originalPopoverBackgroundStyle; // @synthesize originalPopoverBackgroundStyle=_originalPopoverBackgroundStyle;

@property(retain, nonatomic) _UIActivityHelper *activityHelper; // @synthesize activityHelper=_activityHelper;

@property(retain, nonatomic) NSMutableDictionary *activitiesByUUID; // @synthesize activitiesByUUID=_activitiesByUUID;

@property(copy, nonatomic) NSArray *applicationActivities; // @synthesize applicationActivities=_applicationActivities;

@property(copy, nonatomic) NSArray *activityItems; // @synthesize activityItems=_activityItems;

@property(retain, nonatomic, getter=_placeholderViewController, setter=_setPlaceholderViewController:) _UIActivityGroupListViewController *placeholderViewController; // @synthesize placeholderViewController=_placeholderViewController;

@property(nonatomic) _Bool _viewServiceBeganConnecting; // @synthesize _viewServiceBeganConnecting=__viewServiceBeganConnecting;

@property(nonatomic) _Bool shareServicePreferredContentSizeIsValid; // @synthesize shareServicePreferredContentSizeIsValid=_shareServicePreferredContentSizeIsValid;

@property(nonatomic) _Bool waitingForInitialShareServicePreferredContentSize; // @synthesize waitingForInitialShareServicePreferredContentSize=_waitingForInitialShareServicePreferredContentSize;

@property(retain, nonatomic) UISUIActivityViewControllerConfiguration *activityViewControllerConfiguration; // @synthesize activityViewControllerConfiguration=_activityViewControllerConfiguration;

@property(retain, nonatomic) id <_UIShareExtensionService> shareExtensionService; // @synthesize shareExtensionService=_shareExtensionService;

@property(copy, nonatomic) id <NSCopying> extensionRequestIdentifier; // @synthesize extensionRequestIdentifier=_extensionRequestIdentifier;

@property(retain, nonatomic) NSExtension *shareExtension; // @synthesize shareExtension=_shareExtension;

@property(retain, nonatomic) _UIShareExtensionRemoteViewController *remoteContentViewController; // @synthesize remoteContentViewController=_remoteContentViewController;

@property(copy, nonatomic) NSArray *excludedActivityTypes; // @synthesize excludedActivityTypes=_excludedActivityTypes;

@property(copy, nonatomic) CDUnknownBlockType completionWithItemsHandler; // @synthesize completionWithItemsHandler=_completionWithItemsHandler;

@property(copy, nonatomic) CDUnknownBlockType completionHandler; // @synthesize completionHandler=_completionHandler;

- (void).cxx_destruct;

- (void)shareExtensionServiceAirDropActivityDidSuccessfullyCompleteTransfer;

- (void)shareExtensionServiceAirDropActivityDidSuccessfullyStartTransfer;

- (void)_willPerformInServiceActivityType:(id)arg1 activitySpecificMetadata:(id)arg2;

- (void)shareExtensionServiceRequestPerformActivityInHostForExtensionActivityWithBundleIdentifier:(id)arg1;

- (void)shareExtensionServiceRequestPerformActivityInHostForActivityUUID:(id)arg1;

- (void)shareExtensionServiceDidFinishPerformingInServiceActivityWithUUID:(id)arg1 responseData:(id)arg2;

- (void)shareExtensionServiceWillPerformInServiceActivityWithDataRequest:(id)arg1 dismissPresentation:(_Bool)arg2 completion:(CDUnknownBlockType)arg3;

- (void)shareExtensionServiceDisableSheetAvoidsKeyboardUntilContentSizeUpdate;

- (void)shareExtensionServiceChangeSheetDismissButtonHidden:(_Bool)arg1;

- (void)shareExtensionServiceChangeSheetDismissButtonTitle:(id)arg1;

- (void)_shareExtensionServicePreferredContentSizeUpdated:(struct CGSize)arg1;

- (_Bool)_shouldShowSystemActivityType:(id)arg1;

- (_Bool)activityHelper:(id)arg1 matchingWithContext:(id)arg2 shouldIncludeSystemActivityType:(id)arg3;

- (id)_configurationForActivity:(id)arg1;

- (id)_activityConfigurationsForActivities:(id)arg1;

- (id)_newShareUIConfigurationWithMatchingResults:(id)arg1;

- (id)_newShareUIConfigurationForCurrentState;

- (void)_loadActivityViewControllerConfiguration;

- (void)_preheatActivityViewControllerConfiguration;

- (void)_insertIntoActivitiesByUUID:(id)arg1;

- (void)_removeFromActivitiesByUUID:(id)arg1;

- (id)_activityWithActivityUUID:(id)arg1;

- (void)decodeRestorableStateWithCoder:(id)arg1;

- (void)encodeRestorableStateWithCoder:(id)arg1;

- (void)actionSheetPresentationControllerDidDismissActionSheet:(id)arg1;

- (id)visualStyleForAlertControllerStyle:(long long)arg1 traitCollection:(id)arg2 descriptor:(id)arg3;

- (void)presentViewController:(id)arg1 animated:(_Bool)arg2 completion:(CDUnknownBlockType)arg3;

- (void)_cancel;

- (void)_didResignContentViewControllerOfPopover:(id)arg1;

- (void)_setPopoverController:(id)arg1;

- (void)observeValueForKeyPath:(id)arg1 ofObject:(id)arg2 change:(id)arg3 context:(void *)arg4;

- (void)_changeActionSheetAvoidsKeyboardDisabledUntilNextUpdatePreferredContentSize:(_Bool)arg1;

- (void)_changeActionPresentationDismissButtonHidden:(_Bool)arg1;

- (void)_changeActionPresentationDismissButtonTitle:(id)arg1;

- (void)_endDismissalDetectionOfViewControllerForSelectedActivityShouldAutoCancel;

- (void)_presentationControllerDismissalTransitionDidEndNotification:(id)arg1;

- (void)_beginDismissalDetectionOfViewControllerForSelectedActivityShouldAutoCancel;

- (void)_endInProgressActivityExecutionForcedStrongReference;

- (void)_beginInProgressActivityExecutionForcedStrongReference;

- (_Bool)_queueBackgroundOperationsForActivityItems:(id)arg1 activityBeingPerformed:(id)arg2;

- (void)_performActivity:(id)arg1;

- (_Bool)_shouldExecuteItemOperation:(id)arg1 forActivity:(id)arg2;

- (void)_performActivityOfType:(id)arg1 executionEnvironment:(long long)arg2;

- (void)_prepareActivity:(id)arg1 completion:(CDUnknownBlockType)arg2;

- (void)_prepareActivity:(id)arg1;

- (id)_titleForActivity:(id)arg1;

- (void)_resetAfterActivity:(_Bool)arg1;

- (void)_executeActivity;

- (void)_cleanupActivityWithSuccess:(_Bool)arg1;

- (void)_cleanupActivityWithSuccess:(_Bool)arg1 items:(id)arg2 error:(id)arg3;

- (void)_emitInteractionTelemetry:(_Bool)arg1 error:(id)arg2;

- (void)_clearActivity;

- (void)_performDismissWithCompletionHandler:(CDUnknownBlockType)arg1;

- (void)_updateSourceIsManagedForURLs;

- (_Bool)shouldAutorotateToInterfaceOrientation:(long long)arg1;

- (void)viewWillTransitionToSize:(struct CGSize)arg1 withTransitionCoordinator:(id)arg2;

- (void)dismissViewControllerAnimated:(_Bool)arg1 completion:(CDUnknownBlockType)arg2;

- (void)setModalPresentationStyle:(long long)arg1;

- (id)_presentationControllerForPresentedController:(id)arg1 presentingController:(id)arg2 sourceController:(id)arg3;

- (_Bool)_requiresCustomPresentationController;

- (void)_updatePlaceholderPreferredContentSize;

- (void)preferredContentSizeDidChangeForChildContentContainer:(id)arg1;

- (void)viewSafeAreaInsetsDidChange;

- (void)viewDidLayoutSubviews;

- (void)__viewControllerWillBePresented:(_Bool)arg1;

- (void)viewWillDisappear:(_Bool)arg1;

- (void)viewDidAppear:(_Bool)arg1;

- (void)viewWillAppear:(_Bool)arg1;

- (double)_displayHeight;

- (void)_presentationOrEmbeddingDidBegin:(_Bool)arg1;

- (void)_createAndInstallPlaceholderViewControllerIfNeeded;

- (_Bool)_isActionRowExcluded;

- (_Bool)_isSharingRowExcluded;

- (_Bool)_isAirDropExcludedWithActivityItemValues:(id)arg1;

- (_Bool)_shouldIncludeTagsUIPlaceholderWithActivityItemValues:(id)arg1;

- (id)_containedAlertController;

- (void)_shareSheetReadyToInteractAfterCACommit:(_Bool)arg1;

- (void)_removePlaceholderViewControllerIfNeeded;

- (void)_installViewController:(id)arg1;

- (void)_embedRemoteContentViewControllerAndPerformAfterCompletingFencedCommit:(CDUnknownBlockType)arg1;

- (void)viewDidLoad;

- (void)_updateActivityViewControllerConfiguration;

- (void)_updateActivityItems:(id)arg1;

- (id)_newActivityMatchingContext;

- (id)_availableActivities;

- (id)_activityItemValues;

- (id)_securityScopedURLsForMatching;

- (id)_activityItemURLValuesForMatching;

- (id)_placeholderActivityItemValues;

- (void)dealloc;

- (void)_setupLegacyAlertPresentationControllers;

- (void)_preheatActivitiesIfNeeded;

- (void)_shareServiceFinishedInitialPreferredContentSizeUpdate;

- (void)_sendInitialShareServiceConfigurationAndUpdatePreferredContentSize;

- (void)_retryRemoteViewServiceConnectionIfPossibleWithPriming:(_Bool)arg1 previousAttempts:(long long)arg2;

- (void)_connectToRemoteViewServiceOnceWithPriming:(_Bool)arg1 previousAttempts:(long long)arg2;

- (void)_primeExtensionDiscovery;

- (void)_preloadInitialConfigurationLocallyIfNeeded;

- (id)initWithActivityItems:(id)arg1 applicationActivities:(id)arg2;

- (id)initWithCoder:(id)arg1;

- (id)initWithNibName:(id)arg1 bundle:(id)arg2;

- (id)init;

@property(copy, nonatomic) CDUnknownBlockType dismissCompletionHandler;



// Remaining properties

@property(readonly, copy) NSString *debugDescription;

@property(readonly, copy) NSString *description;

@property(readonly) unsigned long long hash;

@property(readonly) Class superclass;



@end

But again, this is only for exploration. You should never rely on this information for production code. (For example, the version of UIKitCore in /System/iOSSupport/System/Library/PrivateFrameworks/ has a smaller list of ivars that doesn't include subject, so this may not even work on all UIKit platforms.)

Unrelated note: the actual property's name is subject, not Subject. You're getting away with this because setValue(_:forKey:) capitalizes the first letter automatically and constructs setSubject:. See the Key-Value Coding Programming Guide for more details about how this works. Generally speaking, KVC is not as commonly used directly in Swift, and setValue(_:forKey:) and other KVC methods should generally be avoided in Swift unless you know what you're doing. They're not type-safe.