I basically want to increment a value on performing an action. So what I'm doing is when the action is performed the first time, I assign the value of 1 to a new property in Realm and then I add it to the realm database.
The second time the action is performed, the max value is taken from all the values in the property and that max value is incremented by 1 and then added to the database.
But what happens is the first time itself, when I reach the line realm.add(chatMsgObj) a crash occurs saying Can only add, remove, or create objects in a Realm in a write transaction - call beginWriteTransaction on an RLMRealm instance first.
This is the code..
func incrementID() -> Int {
let realm = try! Realm()
var myvalue = realm.objects(ChatMessage.self).map{$0.mainId}.max() ?? 1
myvalue = myvalue + 1
chatMsgObj.mainId = myvalue
realm.add(chatMsgObj) //CRASH HERE
return myvalue
}
Can only add, remove, or create objects in a Realm in a write transaction - call beginWriteTransaction on an RLMRealm instance first.
You need to open realm then write.
Read more about realm here, and this code should work for you now.
try! realm.write {
realm.add(chatMsgObj)
}
EDIT: from the comments below you having another problem: which is writing on the same primary key, take a peek into the documentation of realm again, and this could be a configuration problem however,
you can try to delete the application from the (Simulator/Device) that you are testing on it, and rerun the application again.
And you came a cross a
Attempting to create an object of type 'ChatMessage' with an existing
primary key value '0'
so with this new crash you have 2 options.
1- change the PrimaryKey of the new object that it being written.
2- fetch the object of that PrimaryKey and modify it.
Now for the fetching and modifying part, take a peek on this code you should have an idea.
let realm = try! Realm()
let myChatObject = realm.objects(Dog.self).filter("youPrimaryKey == 1").first
try! realm.write {
myChatObject!.something = newValue
}
Related
Say I am creating an object that takes two strings and acts like a dictionary.
class WordInDictionary: Object {
#objc dynamic var word: String = ""
#objc dynamic var meaning: String = ""
What should I do if I wanted to have some initial objects that get added to the database just once upon installation/update of the app?
Also, is there a way to make it so that just those initial objects can't be deleted?
"What should I do if I wanted to have some initial objects that get added to the database just once upon installation/update of the app?"
One option would be to have some code near the realm initialisation that checks if there are any WordInDictionary objects already in the realm - if not then add the required default objects.
E.g.
let realm = try! Realm()
if realm.objects(WordInDictionary.self).isEmpty
{
// Add required words here
}
"Also, is there a way to make it so that just those initial objects can't be deleted?"
I don't know of a way to make realm objects read-only. You'd have to implement this in code in some way, e.g. have a isDeletable boolean member which is true for every user-created object and false for your default members, then only delete those from realm.
E.g. for your deletion code:
func deleteWords(wordsToDelete: Results<WordInDictionary>)
{
try! realm.write
{
realm.delete(wordsToDelete.filter("isDeletable = true")
}
}
I'm using SwiftRealm 2.03 and do not understand the magic how constant data (even metadata) gets updated if the data in realm changes...
Here an example:
private func closePastExistingTravelTimes(){
let travelTimes = fetchTravelTimes(onlyNotClosedTravelTimes: true)
guard travelTimes.count > 1 else {
return
}
let numberOfTravelTimes = travelTimes.count
for index in 0..<numberOfTravelTimes-2{
print("index:\(index) count:\(travelTimes.count)")
try! realm.write {
let travelTime = travelTimes[index]
travelTime.travelPhaseIsClosed = true
realm.add(travelTime, update: true)
}
}
}
I'm loading data in the beginning and store them in an constant.
Then I iterate over the items and change the condition of the query so that the fetched data would change if I would query again. But I don't. What even is more suprising that the constant numberOfTravelTimes is even adjusted as you can see below in the log.
index:0 count:5
index:1 count:4
index:2 count:3
index:3 count:2 --> BAM - Exception
What is happening here? How can I be save in my example?
Realm Results objects are live, meaning if you update an object in such a way that it no longer conforms to a Results query, the Results object will update to exclude it. This means you need to be careful when you base a for loop off a Results object, since if the Results object mutates in the middle of the loop, you'll end up with an exception.
Normally, the easiest, but not the most elegant way to mitigate this is to copy all of the Realm objects in a Results object to a static array so it won't mutate during the loop.
In this particular case however, it would be more appropriate to just enclose the entire for loop inside the Realm write transaction. This is generally best practice (Since it's best to batch as many Realm writes into as few write transactions as possible), but in this case, it will have the added advantage of not updating the contents of the Results object until after you're done with it.
try! realm.write { // Open the Realm write transaction outside of the loop
for index in 0..<numberOfTravelTimes-2 {
print("index:\(index) count:\(travelTimes.count)")
let travelTime = travelTimes[index]
travelTime.travelPhaseIsClosed = true
realm.add(travelTime, update: true)
}
}
You should iterate your results in reverse order.
for index in (0 ..<numberOfTravelTimes-1).reverse()
See if it helps
I'll make it short as possible.
I have an API request that I fetch data from (i.e. Parse).
When I'm getting the results I'm writing it to Realm and then adding them to a UICollectionView's data source.
There are requests that take a bit more time, which run asynchronous. I'm getting the needed results after the data source and collection view was already reloaded.
I'm writing the needed update from the results to my Realm database.
I have read that it's possible to use Realm's Results. But I honestly didn't understood it. I guess there is a dynamic and safe way working with collection views and Realm. Here is my approach for now.
This is how I populate the collection view's data source at the moment:
Declaration
var dataSource = [Realm_item]()
where Realm_item is a Realm Object type.
Looping and Writing
override func viewDidLoad() {
super.viewDidLoad()
for nowResult in FetchedResultsFromAPI
{
let item = Realm_item()
item.item_Title = nowResult["Title"] as! String
item.item_Price = nowResult["Price"] as! String
// Example - Will write it later after the collectionView Done - Async request
GetFileFromImageAndThanWriteRealm(x.image)
// Example - Will write it later after the collectionView Done - Async request
dataSource.append(item)
}
//After finish running over the results *Before writing the image data*
try! self.realm.write {
self.realm.add(self.dataSource)
}
myCollectionView.reloadData()
}
After I write the image to Realm to an already created "object". Will the same Realm Object (with the same primary key) automatically update over in the data source?
What is the right way to update the object from the data source after I wrote the update to same object from the Realm DB?
Update
Model class
class Realm_item: Object {
dynamic var item_ID : String!
dynamic var item_Title : String!
dynamic var item_Price : String!
dynamic var imgPath : String?
override class func primaryKey() -> String {
return "item_ID"
}
}
First I'm checking whether the "object id" exists in the Realm. If it does, I fetch the object from Realm and append it to the data source. If it doesn't exist, I create a new Realm object, write it and than appending it.
Fetching the data from Parse
This happens in the viewDidLoad method and prepares the data source:
var query = PFQuery(className:"Realm_item")
query.limit = 100
query.findObjectsInBackgroundWithBlock { (respond, error) -> Void in
if error == nil
{
for x in respond!
{
if let FetchedItem = self.realm.objectForPrimaryKey(Realm_item.self, key: x.objectId!)
{
self.dataSource.append(FetchedItem)
}
else
{
let item = Realm_item()
item.item_ID = x.objectId
item.item_Title = x["Title"] as! String
item.item_Price = x["Price"] as! String
let file = x["Images"] as! PFFile
RealmHelper().getAndSaveImageFromPFFile(file, named: x.objectId!)
self.dataSource.append(item)
}
}
try! self.realm.write {
self.realm.add(self.dataSource)
}
self.myCollectionView.reloadData()
print(respond?.count)
}
}
Thank you!
You seem to have a few questions and problems here, so I'll do my best.
I suggest you use the Results type as your data source, something like:
var dataSource: Results<Realm_item>?
Then, in your viewDidLoad():
dataSource = realm.objects(Realm_item).
Be sure to use the relevant error checking before using dataSource. We use an optional Results<Realm_item> because the Realm object you're using it from needs to be initialised first. I.e., you'll get something like "Instance member * cannot be used on type *" if you try declaring the results like let dataSource = realm.objects(Realm_item).
The Realm documentation (a very well-written and useful reference to have when you're using Realm as beginner like myself), has this to say about Results...
Results are live, auto-updating views into the underlying data, which means results never have to be re-fetched. Modifying objects that affect the query will be reflected in the results immediately.
Your mileage may vary depending on how you have everything set up. You could try posting your Realm models and Parse-related code for review and comment.
Your last question:
What is the right way to update the "object" from the Data Source after i wrote the update to same object from the Realm DB?
I gather you're asking the best way to update your UI (CollectionView) when the underlying data has been updated? If so...
You can subscribe to Realm notifications to know when Realm data is updated, indicating when your app’s UI should be refreshed for example, without having to re-fetch your Results.
Please, tell me, how to rearrange items of Realm's list of objects by index? I.e. I'm looking something like
let movingElement = array[oldIndex]
array.removeAtIndex(oldIndex)
array.insert(movingElement, atIndex: newIndex)
if it was with a casual Swift array of something.
But for List in Realm I can not do the same thing:
let realm = try! Realm()
var all = try! Realm().objects(element)
realm.write {
all.removeAtIndex() // all of type
Another option is to
let realm = try! Realm()
let element = try! Realm().objects(Element)[oldIndex]
realm.write{
realm.delete(element)
realm.add(...) // How to set index to place new object at?
}
But how to insert element in proper place? May be there is a proper method how to move elements of realm of the same type (class) by index?
Thanks in advance!
You cannot do it with query results, as they are unordered (or in a specific order if you sort them). But if you put them into Realm List (which you can store as member in a Realm object), then you can use both move and swap methods to reorder elements.
Here is the API docs for the the List type: https://realm.io/docs/swift/latest/api/Classes/List.html
I am trying to use Realm for my iOS app. When updating the local Realm DB using createOrUpate, it rewrites the unprovided properties with default values, rather than keep them unchanged. The Realm I use is up to date, 0.93. Anybody has the same issue?
let realm = RLMRealm.defaultRealm()
realm.beginWriteTransaction()
for matchedUser in matchedUsers {
let newMatchedUser = MatchedUser()
newMatchedUser.objectId = matchedUser.objectId
newMatchedUser.username = matchedUser.username
newMatchedUser.email = matchedUser.email
newMatchedUser.fullname = matchedUser["fullname"] as! String
//they are other properties unprovided here.
MatchedUser.createOrUpdateInDefaultRealmWithValue(newMatchedUser)
}
realm.commitWriteTransaction()
So, I figured out what the issue was. It turns out you cannot user newMachtedUser to update the DB because it will initialize it first and the default values will be provided for this initialization process. The right way is to using individual values to update, or create an dictionary/array for that update.