删除所有未来出现的 Realm 对象的正确方法是什么？

Question

目前，我正在使用此代码删除所有未来的重复交易：

let futureRecurringTransactions = self.transactions.filter(NSPredicate(format: "transactionDescription == %@ && transactionDate >= %@ && transactionCategory == %@", transaction!.transactionDescription!, transaction!.transactionDate as CVarArg, transaction!.transactionCategory!))
            
            for transaction in futureRecurringTransactions {
                try! self.realm.write {
                    self.realm.delete(transaction)
                }
            }

这是我的 Realm 数据模型：

import RealmSwift

class Transaction: Object {
    
    @objc dynamic var transactionDescription: String? = nil
    @objc dynamic var transactionAmount = 0.0
    @objc dynamic var transactionDate = Date()
    @objc dynamic var transactionCategory: Category? = nil
    @objc dynamic var repeatInterval = ""
    @objc dynamic var isCleared = false
    @objc dynamic var transactionName = ""
    @objc dynamic var transactionID = UUID().uuidString
    
    convenience init(theDate: Date) {
        self.init()
        self.transactionDate = theDate
    }
    
    override static func primaryKey() -> String? {
        return "transactionID"
    }
        
}

代码有效，但感觉我这样做的方式很业余而且笨拙。有没有更好更准确更妥当的方法？

我认为使用 transactionID 可能会很好，但每个交易都有一个唯一的 transactionID，所以我不确定它是如何工作的。

Answer 1

我通常做的是为每个要放置在集合上的约束创建一个唯一的 NSPredicate。您可以混合和匹配每个谓词以形成一组独特的过滤器。例如：

extension NSPredicate {
    static func transactionDescriptionEqualTo(_ description: String?) -> NSPredicate {
        if let description = description {
            return .init(format: "transactionDescription == %@", description)
        }
        return .init(format: "transactionDescription == nil")
    }

    static func transactionCategoryEqualTo(_ category: Category?) -> NSPredicate {
        if let category = category {
            return .init(format: "transactionCategory == %@", category)
        }
        return .init(format: "transactionCategory == nil")
    }

    static func transactionDateIsAfter(_ date: Date) -> NSPredicate {
        return .init(format: "transactionDate >= %@", date as NSDate)
    }

    static func transactionIDNotEqualTo(_ id: String) -> NSPredicate {
        return .init(format: "transactionID != %@", id)
    }

    static func futureRepeats(of transaction: Transaction) -> NSPredicate {
        return NSCompoundPredicate(andPredicateWithSubpredicates: [
            .transactionDescriptionEqualTo(transaction.transactionDescription),
            .transactionCategoryEqualTo(transaction.transactionCategory),
            .transactionDateIsAfter(transaction.transactionDate),
            .transactionIDNotEqualTo(transaction.transactionID),
        ])
    }
}

另请注意，您无需遍历结果。您可以像这样删除结果中的所有对象：

let realm = try Realm()
try realm.write {
    realm.delete(transactions.filter(.futureRepeats(of: transaction)))
}

最后，将 transactionID 作为约束包括在内是个好主意。否则原始交易将包含在结果中。

删除所有未来出现的 Realm 对象的正确方法是什么？

What's the correct way to delete all future occurrences of a Realm object?

for-loop

crud

realm

swift