static let sharedInstance not accessible from Objective-C code

Question

Problem:

The declared static let sharedInstance is not accessible from Objective-C code when building the main app target.

Code:

    @objc public protocol ManagedObjectContextProvider {
          var context: NSManagedObjectContext { get }
    }

@objc public final class ManagedObjectContextProviderImpl: NSObject, ManagedObjectContextProvider {
    public static let sharedInstance: ManagedObjectContextProvider = ManagedObjectContextProviderImpl()
    
    override private init() {}
    
    public var context: NSManagedObjectContext {
        return NSManagedObjectContext.mr_default()
    }
}

Context:

This file is contained in 2 targets [main iOS App and Share extension]

In the swift to objc generated header of the main app the interface of the swift class is generated as follows:

  @class NSManagedObjectContext;

  SWIFT_PROTOCOL("_TtP4<#MyAppName#>28ManagedObjectContextProvider_")
  @protocol ManagedObjectContextProvider
  @property (nonatomic, readonly, strong) NSManagedObjectContext * _Nonnull context;
  @end


  SWIFT_CLASS("_TtC4<#MyAppName>32ManagedObjectContextProviderImpl")
  @interface ManagedObjectContextProviderImpl : NSObject <ManagedObjectContextProvider>
  - (nonnull instancetype)init SWIFT_UNAVAILABLE;
  @property (nonatomic, readonly, strong) NSManagedObjectContext * _Nonnull context;
  @end

In the swift to objc generated header of the share extension the interface of the swift class is generated correctly and is:

  @class NSManagedObjectContext;

  SWIFT_PROTOCOL("_TtP4<MyAppName>28ManagedObjectContextProvider_")
  @protocol ManagedObjectContextProvider
  @property (nonatomic, readonly, strong) NSManagedObjectContext * _Nonnull context;
  @end


  SWIFT_CLASS("_TtC4<MyAppName>32ManagedObjectContextProviderImpl")
  @interface ManagedObjectContextProviderImpl : NSObject <ManagedObjectContextProvider>
  SWIFT_CLASS_PROPERTY(@property (nonatomic, class, readonly, strong)       id <ManagedObjectContextProvider> _Nonnull sharedInstance;)
  + (id <ManagedObjectContextProvider> _Nonnull)sharedInstance SWIFT_WARN_UNUSED_RESULT;
  - (nonnull instancetype)init SWIFT_UNAVAILABLE;
  @property (nonatomic, readonly, strong) NSManagedObjectContext * _Nonnull context;
   @end

MyAppName specified above is the module name used when generating the Swift to Obj-C header and is the same for both main target and share extension

What I've tried:

Copy the same class declaration in both headers [tricks the compiler but fails at runtime with "unrecognized selector"]
Modify the module name of the extension so that it would have a diff module name than the target

What not to propose as a solution:

To use a different module instead of files belonging to 2 targets

@PPL, I don't think the scope of that answer is valid anymore with latest swift. I can reach the shared instance when working with my shared extension target even if it is declared as a static let. My problem is I cannot reach it when building the main target. — Fawkes
– Fawkes, Commented Feb 27, 2018 at 10:37
@MilanNosáľ, works with objcMembers. Please propose it as a solution and would be nice if you include a short explanation or direct link to Apple docs regarding usage of objcMembers. Thank you! — Fawkes
– Fawkes, Commented Feb 27, 2018 at 10:43

Milan Nosáľ · Accepted Answer · 2018-02-27 10:47:58Z

6

To make members (also static) accessible to ObjC code, you need to add @objc modifier to them, or @objcMembers modifier to class (which is a syntactic sugar to marking all the members with @objc). Read more in documentation.

answered Feb 27, 2018 at 10:47

Milan Nosáľ

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1 Comment

Fawkes Over a year ago

I guess the extension module swift version is "3" thus this works for the extension while the main target's swift version is "4" and it no longer generates the interface for all the members of the class if objcMembers is not added. Thank you for the answer.

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