generic.m

#import <Foundation/Foundation.h>


#define GENERIC(type, parameterType) __typeof__(type (^)(parameterType))
#define GENERIC_DERIVED_TYPE(genericObject) __typeof__(genericObject(NULL))


@interface MAList : NSObject

- (id)initWithArray: (NSArray *)array;

- (id)get: (NSUInteger)index;

@end

@implementation MAList {
    NSArray *_array;
}

- (id)initWithArray: (NSArray *)array {
    _array = [array copy];
    return self;
}

- (id)get: (NSUInteger)index {
    return _array[index];
}

@end

#define MAList(type) GENERIC(type, void *)
#define MAListGet(list, index) (GENERIC_DERIVED_TYPE(list))[list get: index]


int main(int argc, char **argv) {
    @autoreleasepool {
        MAList(NSString *) list = (MAList(NSString *))[[MAList alloc] initWithArray: @[ @"hello", @"world" ]];
        NSString *first = MAListGet(list, 0);
        NSNumber *second = MAListGet(list, 1);
        NSLog(@"hi %@", list);
    }
}