Utilize an NSBlock within the framework of JavaScriptCore as a property

Question

Utilize an NSBlock within the framework of JavaScriptCore as a property

Is there a way to use NSBlock as a property that is changeable in JavaScript?

@protocol ExportingUser <NSObject, JSExport>

@property (nonatomic, copy) void (^changedName) (void);

@property (nonatomic) NSString* name;

@end

I am trying to call changedName from Obj-C, a function whose definition originates from JavaScript. For example:

user.name = "Peyman"; // this will update the name property in Obj-C.

user.changedName = function() { console.log("yay"); } // but this does not work

I am aware of using JSValue's callWithArguments method, but I would prefer an alternate solution if available.

Edit: Upon further consideration, it seems that the callWithArguments method may not be suitable. This is because objects bound to Objective-C classes are not extendable in JavaScript, meaning any new additions would be ignored.

javascript ios objective-c javascriptcore

Answer 1

Answer №1

The information provided in JSValue.h is essential:

//   Objective-C type  |   JavaScript type
// --------------------+---------------------
//         nil         |     undefined
//        NSNull       |        null
//       NSString      |       string
//       NSNumber      |   number, boolean
//     NSDictionary    |   Object object
//       NSArray       |    Array object
//        NSDate       |     Date object
//       NSBlock *     |   Function object *
//          id **      |   Wrapper object **
//        Class ***    | Constructor object ***
//
// * Instances of NSBlock with supported arguments types will be presented as
// callable Function objects to JavaScript. For more details on supported argument
// types, refer to JSExport.h. If a JavaScript Function derived from an Objective-C
// block gets converted back to an Objective-C object, the block itself will be returned.
// All other JavaScript functions will be changed similarly to a JavaScript object of type Object.

It appears that you can use the following code snippet:

@property (nonatomic, copy) JSValue* modifiedName;

Then, when you need to invoke the function:

typedef void (^nameModifiedBlock)(void);

modifiedNameObject = [self.modifiedName toObject];

if ([modifiedNameObject isKindOfClass: NSClassFromString(@"NSBlock")]){
   ((nameModifiedBlock)modifiedNameObject)();
}

Answer 2

The information provided in JSValue.h is essential:

//   Objective-C type  |   JavaScript type
// --------------------+---------------------
//         nil         |     undefined
//        NSNull       |        null
//       NSString      |       string
//       NSNumber      |   number, boolean
//     NSDictionary    |   Object object
//       NSArray       |    Array object
//        NSDate       |     Date object
//       NSBlock *     |   Function object *
//          id **      |   Wrapper object **
//        Class ***    | Constructor object ***
//
// * Instances of NSBlock with supported arguments types will be presented as
// callable Function objects to JavaScript. For more details on supported argument
// types, refer to JSExport.h. If a JavaScript Function derived from an Objective-C
// block gets converted back to an Objective-C object, the block itself will be returned.
// All other JavaScript functions will be changed similarly to a JavaScript object of type Object.

It appears that you can use the following code snippet:

@property (nonatomic, copy) JSValue* modifiedName;

Then, when you need to invoke the function:

typedef void (^nameModifiedBlock)(void);

modifiedNameObject = [self.modifiedName toObject];

if ([modifiedNameObject isKindOfClass: NSClassFromString(@"NSBlock")]){
   ((nameModifiedBlock)modifiedNameObject)();
}

Utilize an NSBlock within the framework of JavaScriptCore as a property

Answer №1

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