使用Realm查询返回唯一/不同的值

问题描述

我有一个 Message / RLMObject 模型，它有一个 NSString * jabberID 属性/行，我想要检索该行中的每个唯一值。

I have a Message/RLMObject model that has a NSString *jabberID property/row and I want to retrieve every unique value inside that row.

换句话说，我想从我的消息中检索未重复的 jabberID 值型号。任何人都可以帮忙解决这个问题吗？

In other word, I want to retrieve non-repeated jabberID values from my Message model. Can anyone help out figuring this?

我使用coredata的方式是在 NSFetchRequest returnsDistinctResults 设置/ code>。

The way I use to do with coredata was using returnsDistinctResults setting on the NSFetchRequest.

推荐答案

我发现Realm还没有完全支持不同的查询。好消息是我在这个上找到了解决方法。 。

I found out Realm doesn't fully support distinct queries yet. The good news is I also found a workaround for it, on this github issue.

Objective-c

RLMResults *messages = [Message allObjects];
NSMutableArray *uniqueIDs = [[NSMutableArray alloc] init];
NSMutableArray *uniqueMessages  = [[NSMutableArray alloc] init];
for (Message *msg in messages) {
    NSString *jabberID = msg.jabberID;
    Message *uniqueMSG = (Message *)msg;
    if (![uniqueIDs containsObject:jabberID]) {
        [uniqueMessages addObject:uniqueMSG];
        [uniqueIDs addObject:jabberID];
    }
}

Swift 3.0

let realm = try! Realm()
let distinctIDs = Set(realm.objects(Message.self).value(forKey: "jabberID") as! [String])
var distinctMessages = [Message]()
for jabberID in distinctIDs {
    if let message = realm.objects(Message.self).filter("jabberID = '\(jabberID)'").first {
        distinctMessages.append(message)
    }
}

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