同じ処理をテンプレート化

STTemplate.h

#import <Foundation/Foundation.h>

typedef id(^STTemplateBlocks)();
typedef void(^STTemplateBlocksVoid)();

#define STTemplateExecute(instance, aKey, ...) \
    ((STTemplateBlocks)[instance templateOf:aKey])(__VA_ARGS__)
#define STTemplateApply(instance, aKey, ...) \
    ((STTemplateBlocksVoid)[instance templateOf:aKey])(__VA_ARGS__)

@interface STTemplate : NSObject

+ (id)appearance;
+ (id)logic;

- (void)addTemplate:(STTemplateBlocks)block forKey:(NSString *)aKey;
- (STTemplateBlocksVoid)templateOf:(NSString *)aKey;

@end

STTemplate.m

#import "STTemplate.h"

@interface STTemplate ()
@property (strong, nonatomic) NSMutableDictionary *templates;
@end

@implementation STTemplate

+ (id)appearance
{
    static id instance;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [[self alloc] init];
    });
    return instance;
}

+ (id)logic
{
    static id instance;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [[self alloc] init];
    });
    return instance;
}

- (id)init
{
    self = [super init];
    if (self) {
        self.templates = [NSMutableDictionary dictionary];
    }
    return self;
}

- (void)addTemplate:(STTemplateBlocks)block forKey:(NSString *)aKey
{
    NSAssert(block, @"block must be non null!");
    id inBlock = block();
    NSAssert(inBlock, @"block must be non null!");
    id copiedBlock = [inBlock copy];
    [self.templates setObject:copiedBlock forKey:aKey];
}

- (STTemplateBlocksVoid)templateOf:(NSString *)aKey
{
    id block = [self.templates objectForKey:aKey];
    NSAssert(block, @"template is not registered!");
    return block;
}

@end