ios - 如何绑定(bind) Realm 对象的变化？

Question

在我的项目中，我试图通过 MVVM 工作， 所以在 VM 中的 .h 文件

  @property (nonatomic, strong) NSArray    *cities;

在.m文件中

  - (NSArray *)cities {
        return [[GPCity allObjects] valueForKey:@"name"];
    }

GPCity 是 RLMObject 的子类 如何通过 ReactiveCocoa 绑定(bind)它(我的意思是查看所有城市更新/添加/删除)？

类似于:

RAC(self, cities) = [[GPCity allObjects] map:(GPCity *)city {return city.name;}];

Answer 1

您可以将 Realm 更改通知包装在 RAC 信号中:

@interface RLMResults (RACSupport)
- (RACSignal *)gp_signal;
@end

@implementation RLMResults (RACSupport)
- (RACSignal *)gp_signal {
    return [RACSignal createSignal:^(id<RACSubscriber> subscriber) {
        id token = [self.realm addNotificationBlock:^(NSString *notification, RLMRealm *realm) {
            if (notification == RLMRealmDidChangeNotification) {
                [subscriber sendNext:self];
            }
        }];

        return [RACDisposable disposableWithBlock:^{
            [self.realm removeNotification:token];
        }];
    }];
}
@end

然后做:

RAC(self, cities) = [[[RLMObject allObjects] gp_signal]
                     map:^(RLMResults<GPCity *> *cities) { return [cities valueForKey:@"name"]; }];

不幸的是，这将在每次 写入事务后更新信号，而不仅仅是修改城市的事务。一旦 Realm 0.98 发布 support for per-RLMResults notifications ，您将能够执行以下操作，这只会在 GPCity 对象更新时更新:

@interface RLMResults (RACSupport)
- (RACSignal *)gp_signal;
@end

@implementation RLMResults (RACSupport)
- (RACSignal *)gp_signal {
    return [RACSignal createSignal:^(id<RACSubscriber> subscriber) {
        id token = [self addNotificationBlock:^(RLMResults *results, NSError *error) {
            if (error) {
                [subscriber sendError:error];
            }
            else {
                [subscriber sendNext:results];
            }
        }];

        return [RACDisposable disposableWithBlock:^{
            [token stop];
        }];
    }];
}
@end