swift - 可选属性的 Realm Swift 复合键

Question

有什么方法可以为具有可选属性的 Realm 类创建复合键吗？

例如:

class Item: Object {
    dynamic var id = 0
    let importantNumber = RealmOptional<Int>()
    let importantNumber2 = RealmOptional<Int>()

    func setCompoundID(id: Int) {
        self.id = id
        compoundKey = compoundKeyValue()
    }

    func setCompoundImportantNumber(importantNumber: Int) {
        self.importantNumber = importantNumber
        compoundKey = compoundKeyValue()
    }

    func setCompoundImportantNumber2(importantNumber2: Int) {
        self.importantNumber2 = importantNumber2
        compoundKey = compoundKeyValue()
    }

    dynamic lazy var compoundKey: String = self.compoundKeyValue()

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

    func compoundKeyValue() -> String {
        return "\(id)\(importantNumber)\(importantNumber2)"
    }
}

当我这样写我的代码时，编译器提示说我不能为我的常量属性赋值，它建议我将“let”更改为“var”；然而，根据Realm Swift Documentation ，我需要将可选属性设置为常量。

我不确定这是否可行，因为我在 Realm 文档中找不到任何关于可选主键的信息。

Answer 1

您需要设置RealmOptional 的value 成员。 RealmOptional 属性不能是 var，因为 Realm 无法检测对 Objective-C 运行时无法表示的属性类型的分配，这就是为什么 RealmOptional、List 和 LinkingObjects 属性都必须是 let。

class Item: Object {
    dynamic var id = 0
    let importantNumber = RealmOptional<Int>()
    let importantNumber2 = RealmOptional<Int>()

    func setCompoundID(id: Int) {
        self.id = id
        compoundKey = compoundKeyValue()
    }

    func setCompoundImportantNumber(importantNumber: Int) {
        self.importantNumber.value = importantNumber
        compoundKey = compoundKeyValue()
    }

    func setCompoundImportantNumber2(importantNumber2: Int) {
        self.importantNumber2.value = importantNumber2
        compoundKey = compoundKeyValue()
    }

    dynamic lazy var compoundKey: String = self.compoundKeyValue()

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

    func compoundKeyValue() -> String {
        return "\(id)\(importantNumber)\(importantNumber2)"
    }
}