使用Realm数据库向Table View添加条目时出现重复存储问题

Hey there! The root cause of your duplicate entries is that you're reusing the same RealmEventItem instance every time you add a new event. Let's break down what's happening and fix it step by step.

The Problem with Your Current Code #

Right now, every time you tap "Add", you're modifying the existing self.realmEventItem (which is already saved in Realm) and then trying to insert it again with realm.create(...). Since this object is already managed by Realm, this doesn't create a new entry—it either throws an error (hidden by your try!) or causes unexpected behavior like overwriting existing entries and duplicating them on app restart.

The Fix: Create a New Instance for Each Event #

You need to initialize a brand new RealmEventItem every time you add a new event. Here's the revised code for your "Add" action:

newEventAlert.addAction(PMAlertAction(title: "Add", style: .default, action: { 
    print("Add Event Button Pressed in Alert")
    
    // First, validate all required inputs
    guard let eventName = self.nameOfEvent.text, !eventName.isEmpty,
          let dayText = self.dayOfEvent.text, !dayText.isEmpty,
          let monthText = self.monthOfEvent.text, !monthText.isEmpty else {
        print("Missing Information!")
        return
    }
    
    // Create a NEW RealmEventItem instance for the new event
    let newEvent = RealmEventItem()
    newEvent.nameOfEventRealm = eventName
    newEvent.dateOfEventRealm = "\(dayText) \(monthText)"
    newEvent.oneDayBeforeReminderRealm = self.oneDayReminder.text == "Yes"
    newEvent.sevenDaysBeforeReminderRealm = self.sevenDayReminder.text == "Yes"
    
    // Save the new event to Realm
    do {
        try realm.write {
            realm.add(newEvent) // Use add() for new unmanaged objects
        }
    } catch {
        print("Failed to save event: \(error.localizedDescription)")
        return
    }
    
    // Update the table view to show the new entry
    let newIndexPath = IndexPath(row: self.realmEventList.count - 1, section: 0)
    self.tableView.insertRows(at: [newIndexPath], with: .automatic)
    
    self.labelWhenTableViewIsEmpty.text = ""
    print("Added to Table View | Total events: \(self.realmEventList.count)")
    
    // Reset inputs and pickers
    self.nameOfEvent.text = ""
    self.dayPickerView.selectRow(0, inComponent: 0, animated: false)
    self.monthPickerView.selectRow(0, inComponent: 0, animated: false)
    self.oneDayPickerView.selectRow(0, inComponent: 0, animated: false)
    self.sevenDayPickerView.selectRow(0, inComponent: 0, animated: false)
    
    print("All Realm events: \(realm.objects(RealmEventItem.self))")
}))

Key Changes Explained #

• New Instance per Event: We create newEvent as a fresh RealmEventItem instead of reusing self.realmEventItem. This ensures we're adding a completely new entry to Realm.
• Input Validation First: We moved the input check to the top using guard—this exits early if any required field is empty, making the code cleaner and more efficient.
• Safe Error Handling: Replaced try! with do-catch to handle Realm write errors gracefully, avoiding silent crashes that are hard to debug.
• Correct Realm Method: Used realm.add(newEvent) instead of create—add() is designed for inserting new unmanaged objects, while create() is meant for updating existing objects (when using a primary key) or creating unique entries.

Extra Tips to Avoid Future Issues #

• Define a Primary Key (If Needed): If you want to prevent duplicate events with the same name, add a primary key to your RealmEventItem model:

  class RealmEventItem: Object {
      @Persisted(primaryKey: true) var nameOfEventRealm: String
      // ... other properties ...
  }
  

  Then you can use realm.create(RealmEventItem.self, value: newEvent, update: .all) to either create a new event or update an existing one with the same name.
• Avoid Reusing Managed Objects: Never modify a managed Realm object (one that's already saved) unless you intend to update the existing entry in the database.

内容的提问来源于stack exchange，提问作者LearningCoding18