swift - Realm.create 会用相同的主键更新对象吗？

Question

我很好奇，如果我调用 realm.create，它会自动从 Realm 结果更新 Realm 对象吗？

// Assuming a "Book" with a primary key of `1` already exists.
try! realm.write {
realm.create(Book.self, value: ["id": 1, "price": 9000.0], update:   true)
// the book's `title` property will remain unchanged.
}

目前看来我需要再次从 Realm 读取以获取最新的对象。如果我错了，请纠正我。

谢谢

Answer 1

是的，在调用 Realm.create(_:value:update:) 时指定 update: true 将导致更新现有对象。

这是一个基于您提供的代码的片段，用于演示这一点:

class Book: Object {
    dynamic var id = ""
    dynamic var title = ""
    dynamic var price = 0.0

    override class func primaryKey() -> String? { return "id" }
}


let realm = try! Realm()
let book = Book(value: ["1", "To Kill a Mockingbird", 9.99])
try! realm.write {
    realm.add(book)
}

let results = realm.allObjects(ofType: Book.self)

try! realm.write {
    realm.createObject(ofType: Book.self, populatedWith: ["id": "1", "price": 7.99], update: true)
}

print(book)
print(results)

此代码产生以下输出:

Book {
    id = 1;
    title = To Kill a Mockingbird;
    price = 7.99;
}
Results<Book> (
    [0] Book {
        id = 1;
        title = To Kill a Mockingbird;
        price = 7.99;
    }
)

如您所见，现有对象的 price 属性已更新为新值。