NewClass.h

@import Foundation;

NS_ASSUME_NONNULL_BEGIN

@interface NewClass : NSObject

- (instancetype)initWithString:(NSString *)string NS_DESIGNATED_INITIALIZER;

@end

@interface NewClass (Unavailable)

- (instancetype)init NS_UNAVAILABLE;

@end

NS_ASSUME_NONNULL_END

NewClass.m

#import "NewClass.h"

@implementation NewClass

- (instancetype)init {
  __builtin_unreachable();
}

- (instancetype)initWithString:(NSString *)string {
  if ((self = [super init])) {
  }

  return self;
}

@end