Delphi + iOS: Error by "translating" of "UIContextualAction" interface from ObjectiveC to Delphi

Question

i'm trying to add swap actions for UITableView in Delphi by imlement two UITableView delegate methods available from iOS 11:

leadingSwipeActionsConfigurationForRowAtIndexPath trailingSwipeActionsConfigurationForRowAtIndexPath

ObjectiveC:

- (nullable UISwipeActionsConfiguration *)tableView:(UITableView *)tableView leadingSwipeActionsConfigurationForRowAtIndexPath:(NSIndexPath *)indexPath API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos);
- (nullable UISwipeActionsConfiguration *)tableView:(UITableView *)tableView trailingSwipeActionsConfigurationForRowAtIndexPath:(NSIndexPath *)indexPath API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos);

The actions derives from the new class UIContextualAction. My problem is exactly in the translation of this class. Here is the ObjectiveC class definition:

@class UIContextualAction;

// call the completionHandler to reset the context to its normal state (e.g. when swiping, resets to unswiped state)
// pass YES to the completionHandler if the action was actually performed, to show a visual indication of the successful completion

typedef void (^UIContextualActionHandler)(UIContextualAction *action, __kindof UIView *sourceView, void(^completionHandler)(BOOL actionPerformed));

typedef NS_ENUM(NSInteger, UIContextualActionStyle) {
    UIContextualActionStyleNormal,
    UIContextualActionStyleDestructive
} NS_SWIFT_NAME(UIContextualAction.Style) API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos);

UIKIT_EXTERN API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos)
@interface UIContextualAction : NSObject

+ (instancetype)contextualActionWithStyle:(UIContextualActionStyle)style title:(nullable NSString *)title handler:(UIContextualActionHandler)handler;

@property (nonatomic, readonly) UIContextualActionStyle style;
@property (nonatomic, copy, readonly) UIContextualActionHandler handler;

@property (nonatomic, copy, nullable) NSString *title;
@property (nonatomic, copy, nullable) UIColor *backgroundColor; // a default background color is set from the action style
@property (nonatomic, copy, nullable) UIImage *image;

@end

Accordingly, my Delphi import looks like this:

const
  UIContextualActionStyleNormal = 0;
  UIContextualActionStyleDestructive = 1;

type
  UIContextualActionStyle = integer;

  UIContextualActionClass = interface(NSObjectClass)
    ['{F341A178-2950-4D0A-9EF2-DCDEAB76FF81}']
    function contextualActionWithStyle(style: UIContextualActionStyle; title: NSString; handler: Pointer{UIContextualActionHandler}): Pointer; cdecl;
  end;

  UIContextualAction = interface(NSObject)
    ['{C5B4CB53-0655-41FA-B48E-D4FB0E9A54FB}']
    function title: NSString; cdecl;
    function backgroundColor: UIColor; cdecl;
    function image: UIImage; cdecl;
    function style: UIContextualActionStyle;
    function handler: Pointer{UIContextualActionHandler};
    procedure setTitle(title: NSString); cdecl;
    procedure setBackgroundColor(backgroundColor: UIColor); cdecl;
    procedure setImage(image: UIImage); cdecl;
    procedure setStyle(style: UIContextualActionStyle); cdecl;
    procedure setHandler(handler: Pointer{UIContextualActionHandler}); cdecl;
  end;
  TUIContextualAction = class(TOCGenericImport<UIContextualActionClass, UIContextualAction>);

I didn't even come to the implementation of the UIContextualActionHandler and create my action with nil as UIContextualActionHandler for the moment. The app crashes if I want to create an "empty" action:

var
  btnDelete: UIContextualAction;
begin
  //Crash by this code line:
  btnDelete := TUIContextualAction.Wrap(TUIContextualAction.OCClass.contextualActionWithStyle(UIContextualActionStyleNormal, StrToNSStr('Delete'), nil));

What am I doing wrong? Thanks!

The documentation does not say you can pass nil (except it might allow you to anyway). Have you tried supplying a handler? — Dave Nottage, Dec 27 '17 at 09:39
@DaveNottage No, but Xcode test app have no problem with nil as handler. I’m trying to create the handler now. The handler seems like an anonymous method that still have an another anonymous method as parameter. Do You have any idea how i can get it in Delphi? — vitaliy-zh, Dec 27 '17 at 09:58

score 0 · Accepted Answer · answered Dec 27 '17 at 11:20

Solution:

@property (nonatomic, readonly) UIContextualActionStyle style;
@property (nonatomic, copy, readonly) UIContextualActionHandler handler;

are ReadOnly and don't have to be declared. Correct definition:

  UIContextualActionClass = interface(NSObjectClass)
    ['{F341A178-2950-4D0A-9EF2-DCDEAB76FF81}']
    function contextualActionWithStyle(style: UIContextualActionStyle; title: NSString; handler: Pointer{UIContextualActionHandler}): Pointer; cdecl;
  end;

  UIContextualAction = interface(NSObject)
    ['{C5B4CB53-0655-41FA-B48E-D4FB0E9A54FB}']
    function title: NSString; cdecl;
    function backgroundColor: UIColor; cdecl;
    function image: UIImage; cdecl;
    procedure setTitle(title: NSString); cdecl;
    procedure setBackgroundColor(backgroundColor: UIColor); cdecl;
    procedure setImage(image: UIImage); cdecl;
  end;

Delphi + iOS: Error by "translating" of "UIContextualAction" interface from ObjectiveC to Delphi

1 Answers1