Realm.io 和复合主键

Question

我正在为 Swift 1.2 使用 Realm，我想知道如何为实体实现复合主键。

因此您通过覆盖 primaryKey()

来指定您的主键

override static func primaryKey() -> String? { // <--- only 1 field
    return "id"
}

我能看到的唯一方法是像这样创建另一个复合属性

var key1 = "unique thing"
var key2 = 123012

lazy var key: String? = {
    return "\(self.key1)\(self.key2)"
}()

override static func primaryKey() -> String? {
    return "key"
}

如何在 Realm 中正确提供复合键？

Answer 1

这似乎是在 Realm 中 return 复合键的正确方法。

这是来自 Realm 的答案：https://github.com/realm/realm-cocoa/issues/1192

You could use a mix of lazy and didSet instead to have the compoundKey property be both derived and stored:

public final class Card: Object {
    public dynamic var id = 0 {
        didSet {
            compoundKey = compoundKeyValue()
        }
    }
    public dynamic var type = "" {
        didSet {
            compoundKey = compoundKeyValue()
        }
    }
    public dynamic lazy var compoundKey: String = self.compoundKeyValue()
    public override static func primaryKey() -> String? {
        return "compoundKey"
    }

    private func compoundKeyValue() -> String {
        return "\(id)-\(type)"
    }
}

// Example

let card = Card()
card.id = 42
card.type = "yolo"
card.compoundKey // => "42-yolo"

Answer 2

正确答案需要更新（关于 didSet 和 lazy）

取自 "mrackwitz" 领域 git-hub: https://github.com/realm/realm-cocoa/issues/1192 :

public final class Card: Object {
    public dynamic var id = 0
    public func setCompoundID(id: Int) {
        self.id = id
        compoundKey = compoundKeyValue()
    }
    public dynamic var type = ""
    public func setCompoundType(type: String) {
        self.type = type
        compoundKey = compoundKeyValue() 
    }
    public dynamic var compoundKey: String = "0-"
    public override static func primaryKey() -> String? {
        return "compoundKey"
    }

    private func compoundKeyValue() -> String {
        return "\(id)-\(type)"
    }
}

Realm.io 和复合主键

Realm.io and compound primary keys

entity

realm

ios

swift