iphone - 如何在 Realm Swift 中更新对象

Question

我正在尝试学习如何使用 Realm Swift 和 Charts，这样我最终就可以在我正在构建的应用程序中使用它们，并且我在弄清楚 Realm 上花了很多时间。最终，我计划让图表查看我的 Realm 数据库，然后根据数据显示图表，但在此之前，我需要检查 Realm 对象是否存在，如果不存在，创建它，然后当用户使用该应用程序时，向该记录添加“计数”并相应地更新图表。

随着我的学习，我已将其分解为多个步骤。我已经弄清楚如何检查记录是否存在，如果不存在则按如下方式构建:

我的 Realm 模型:

class WorkoutsCount: Object{    
    dynamic var date: Date = Date()
    dynamic var count: Int = Int(0)
}

// function to check if this weeks days have been created in Realm DB yet and creates them if not
    let realm = try! Realm()
    lazy var workouts: Results<WorkoutsCount> = { self.realm.objects(WorkoutsCount.self)}()
    let startOfWeekDate = Date().startOfWeek(weekday: 1)
    let nextDay = 24 * 60 * 60
          
    // checks the DB to see if it contains the start of this week
    func searchForDB(findDate: Date) -> WorkoutsCount?{
        let predicate = NSPredicate(format: "date = %@", findDate as CVarArg)
        let dateObject = self.realm.objects(WorkoutsCount.self).filter(predicate).first
        
        if dateObject?.date == findDate{
            return dateObject
        }
        return nil
    }

    func setThisWeeksDays(){
        //if the beginning of this week doesn't exist in the DB then create each day with 0's as the count data
        if searchForDB(findDate: startOfWeekDate) == nil{
            try! realm.write() {
                
                let defaultWorkoutDates = [startOfWeekDate, startOfWeekDate + TimeInterval(nextDay), startOfWeekDate + TimeInterval(nextDay*2), startOfWeekDate + TimeInterval(nextDay*3), startOfWeekDate + TimeInterval(nextDay*4), startOfWeekDate + TimeInterval(nextDay*5), startOfWeekDate + TimeInterval(nextDay*6)]
                
                for workouts in defaultWorkoutDates {
                    let newWorkoutDate = WorkoutsCount()
                    newWorkoutDate.date = workouts
                    self.realm.add(newWorkoutDate)
                }
            }            
            workouts = realm.objects(WorkoutsCount.self)
        }
    }

我已通过 Realm Browser 应用程序验证了他的工作。

我的待办事项列表中的下一步是弄清楚如何更新“今天的日期记录”的记录。为此，我创建了一个按钮，因此当点击它时，它会尝试执行此操作。我一直在谷歌搜索，并开始认为，由于我在模型中没有使用主键，所以我必须首先删除有问题的特定记录，然后使用新数据再次添加它。我无法根据 Realm 文档甚至更多的谷歌搜索来弄清楚如何做到这一点。这就是我所得到的，尽管它不起作用:

@IBAction func btnUpdate1MW(_ sender: Any) {
        if searchForDB(findDate: today) != nil{
            if plusOne <= 7{
                plusOne += 1
                CounterImage1MW.image = UIImage(named:  "1MWs-done-\(plusOne)")
                
                let realm:Realm = try! Realm()
                
                // deletes the original item prior to being updated and added back below
                let removeTodaysItem = today
                let workout = realm.objects(WorkoutsCount.self).filter("date = '\(removeTodaysItem)'")
                if workout.count > 0{
                    for date in workout{
                        try! realm.write {
                            realm.delete(date)
                        }
                    }
                }
                // adds back the item with an updated count
                do {
                    let realm = try Realm()
                    try realm.write {
                        realm.create(WorkoutsCount.self, value: ["date": today, "count": plusOne], update: false)
                    }
                } catch let error as NSError {
                    fatalError(error.localizedDescription)
                }
            }

            print("add to 1MW + 1")
        }
    }

当我点击 btnUpdate1MW 按钮时，我在 Xcode 中收到以下错误:

Terminating app due to uncaught exception 'Invalid value', reason: 'Expected object of type date for property 'date' on object of type 'WorkoutsCount', but received: 2017-04-24 07:00:00 +0000'

Answer 1

更新对象只是为写入事务中的属性分配一个值。请参阅我们的文档。

https://realm.io/docs/swift/latest/#updating-objects

因此您不需要删除然后添加对象。只需在写入事务中为属性分配新值，如下所示。

let workouts = realm.objects(WorkoutsCount.self).filter("date = %@", removeTodaysItem)

let realm = try! Realm()
if let workout = workouts.first {
    try! realm.write {
        workout.date = today
        workout.count = plusOne
    }
}

仅供引用:请不要在查询中使用字符串插值。一般来说，通过字符串插值构建重要的字符串是不好的做法。使用 NSPredicate 的字符串替换语法，例如 filter("date = %@", removeTodaysItem)。