Objective-C Singleton Pattern for Precompiler

example_usage_class.h

//
//  ExampleUsageService.h
//  ExampleUsage
//
//  Created by Christoph Pageler on 18/03/16.
//  Copyright © 2016 Christoph Pageler. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface ExampleUsageService : NSObject

SINGLETON_INTERFACE

@end

example_usage_class.m

//
//  ExampleUsageService.m
//  ExampleUsage
//
//  Created by Christoph Pageler on 18/03/16.
//  Copyright © 2016 Christoph Pageler. All rights reserved.
//

#import "ExampleUsageService.h"

@implementation ExampleUsageService

SINGLETON_IMPLEMENTATION

@end

interface_or_prefix_header.h

#define SINGLETON_INTERFACE \
- (instancetype)init __attribute__((unavailable("use ´sharedInstance´ instead"))); \
+ (instancetype)sharedInstance; \

#define SINGLETON_IMPLEMENTATION \
+ (instancetype)sharedInstance \
{ \
    static id _sharedInstance = nil; \
    static dispatch_once_t onceToken; \
    dispatch_once(&onceToken, ^{ \
        _sharedInstance = [[[self class] alloc] init]; \
    }); \
    return _sharedInstance; \
} \