跨多个领域的关系？

Question

Realm:

We have the following scenario: There are several stores with employees and customers, several employees that could work at more than one store, and several customers that may shop at several stores. This could be represented with these classes

class Store {
    dynamic var id = ""
    dynamic var address = ""
    let workers = List<Employee>()
    let customers = List<Customer>()
}

class Customer {
    dynamic var id = ""
    dynamic var name = ""
    let stores = LinkingObjects(fromType: Store.self, property: "customers") 
    // ... many more fields about this customer
}

class Employee {
    var id
    var name
    let work = LinkingObjects(fromType: Store.self, property: "workers")
}

The catch here is that we must protect customer information, so none of the customer info can be present in a shared realm and needs to be secure. Neither the store nor Employee data is a security matter. Our current approach is to give each customer their own realm, however, the major drawbacks to this is that requires massive duplication since each customer realm must copy the data of the store. The other drawback is that we would be copying customer data into a shared realm which is a security risk. What would be the best way to architect this scenario that allows for relationships across different Realms?

Answer 1

Realm doesn't currently support "direct" object links across Realms analogous to object properties within the same Realm.

Instead, what I suggest you do is to give your objects primary keys (you can probably just declare your existing id fields as such, or create a new internalId field if your existing id field can't be used for this purpose).

Primary keys are mandatory, must be unique, and can't be changed after they are set, which makes them great for uniquely identifying objects. Our documentation discusses them in greater detail.

Then, instead of directly storing customer info/a customer object in a shared Realm, you can just store the primary keys for the relevant customers, for example in a list. (Right now you'll have to make a wrapper CustomerKey object for example to store the customer's primary key, but we plan to support collections directly containing strings or other primitive types very soon.)

You can enhance this further by adding helper methods on your objects that can be passed in a customer Realm and return the user object (or whatever object's primary key is being stored), looking it up in the Realm automatically. You can use Realm 's object(ofType:forPrimaryKey) method to look up an object based on its primary key.

The main limitation is that you won't get the automatic updating of links you would get with object, list, and LinkingObjects properties. You'll have to manually perform the bookkeeping yourself.

If you have ideas for functionality you want to see in Realm that would go beyond what I've posted here, feel free to share your thoughts at our GitHub issue tracker . We welcome feature requests.