A simple Service Locator pattern for Swift and Obj-c

Registry.h

#import <Foundation/Foundation.h>

#define dep(p) [[Registry shared] resolve: (@protocol(p))]
#define reg(c, p) [[Registry shared] register:[c class] forProtocol:@protocol(p)]

@interface Registry : NSObject
@property (nonatomic, strong)  NSMutableDictionary * _Nonnull classRegister;
@property (nonatomic, strong)  NSMutableDictionary * _Nonnull classInstances;
+(instancetype _Nonnull)shared;
- (id _Nullable)resolve:(Protocol * _Null_unspecified)aProtocol;
- (void)register:(id _Null_unspecified)obj forProtocol:(Protocol * _Null_unspecified)aProtocol;
- (void)releaseAllInstances;
@end

Registry.m

#import "Registry.h"

#define nssfp(p) NSStringFromProtocol(@protocol(p))
#define nssfc(c) NSStringFromClass([c class])

@implementation Registry : NSObject

+ (instancetype _Nonnull)shared
{
    static dispatch_once_t token;
    static id sharedInstance = nil;
    dispatch_once(&token, ^{
        sharedInstance = [[[self class] alloc] init];
    });
    return sharedInstance;
}

- (instancetype)init
{
    self = [super init];
    if (self) {
        _classRegister = [[NSMutableDictionary alloc] init];
        _classInstances = [[NSMutableDictionary alloc] init];
    }
    return self;
}

- (id _Nullable)resolve:(Protocol * _Null_unspecified)aProtocol
{
    NSString *key = NSStringFromProtocol(aProtocol);
    id instance = self.classInstances[key];
    
    if([instance conformsToProtocol:aProtocol])
    {
        return instance;
    }
    else
    {
        NSString *className = self.classRegister[key];
        instance = [[NSClassFromString(className) alloc]init];

        if([instance conformsToProtocol:aProtocol])
        {
            self.classInstances[key] = instance;
            return instance;
        }
    }
    return nil;
}

- (void)register:(id _Null_unspecified)obj forProtocol:(Protocol * _Null_unspecified)aProtocol
{
    NSString *key = NSStringFromProtocol(aProtocol);
    NSString *name = NSStringFromClass([obj class]);
    self.classRegister[key] = name;
}

- (void)releaseAllInstances
{
    self.classInstances = [[NSMutableDictionary alloc] init];
}

@end

Registry.swift

import Foundation

func dep<T>(aProtocol:Protocol) -> T?
{
    return Registry.shared().resolve(aProtocol) as? T
}

func reg(instance: AnyObject, _ aProtocol: Protocol)
{
    Registry.shared().register(instance, forProtocol:aProtocol)
}