An Objective-C pattern for making sum types - ExampleFoo

ExampleFoo.m

#import "ExampleFoo.h" // https://gist.github.com/hborders/094f05d932b3d7a1e389184ba525b0c3
#import "ExamplePrivate.h" // https://gist.github.com/hborders/12fcbe34cf4de68c2317bad92a8e223d

@implementation ExampleFoo
- (instancetype _Nonnull)initPrivate {
  NSLog(@"Unavailable");
  abort();
}
- (instancetype _Nonnull)initWithF:(NSString * _Nonnull)f
                                 g:(NSString * _Nonnull)g {
  NSParameterAssert(f);
  NSParameterAssert(g);
  self = [super initPrivate];
  if (self) {
    _f = f;
    _g = g;
  }
  return self;
}
- (void)switchFoo:(void (^ _Nonnull)(ExampleFoo * _Nonnull foo_))fooBlock
              bar:(void (^ _Nonnull)(ExampleBar * _Nonnull bar_))barBlock {
  NSParameterAssert(fooBlock);
  NSParameterAssert(barBlock);
  [super switchFoo:fooBlock
               bar:barBlock];
  fooBlock(self);
}
@end