Objective-C do not have protected property. The ivars are protected by default, but you still have to declare them in interface file in order to expose those variables. However, that is not what I can use. Because in the case that my private variables are cpp class but I can only expose .h to the header to Swift.

Protected Property

Objective-C do not have protected property. The ivars are protected by default, but you still have to declare them in interface file in order to expose those variables. However, that is not what I can use. Because in the case that my private variables are cpp class but I can only expose .h to the header to Swift.

So Another work around to expose the parent private methods to child classes are using a second header file.

Solution

In Parent.h

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@interface Parent : NSObject
// Public Property and Methods
// ...
@end

In Parent.mm

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#import "Parent.h"
@interface Parent()
// property goes here becomes private
// ...
@end

@implementation Parent

@end

In Child.h

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#import "Parent.h"

@interface Child : Parent
// Public Property and Methods

@end

In Child.mm

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#import "Child.h"

@interface Child()
// private property for child only
// ...
@end

@implementation Child

@end

Above is an example I am going to use. Assume we have some property for Parent that I want to expose to Child only which are protected properties. Here is a step by step solution on how to achieve this.

Create a Second Header For Parent

First step is to create a second Header file for parent.

In Parent_Protected.h

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#import "Parent.h"
@interface Parent()
@property NSInteger protectedInt;
@end

Import into Parent

Import the second header file in Parent.mm

In Parent.mm

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#import "Parent.h"
#import "Parent_Protected.h"

@interface Parent()
// property goes here becomes private
// ...
- (NSInteger)getProtectedInt;
@end

@implementation Parent
- (NSInteger)getProtectedInt {
  return _protectedInt;
}
@end

Import into Child

Import the second header file in Child.mm

In Child.mm

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#import "Child.h"
#import "Parent_Protected.h"

@interface Child()
// private property for child only
// ...
- (NSInteger)getParentInt;
@end

@implementation Child
- (NSInteger)getParentInt {
  return [super protectedInt];
}
@end

Note that you need to use [super xxx] to access the property. If you use _xxx it may end up complain Use of undeclared identifier.