Updating realm list removes others - swift

Question

I am trying to update realm list but for some reason, it deletes last one and adds only new one instead.
This is what I am doing:
if !RealmService.shared.ifPortfolioExists(name: newPortfolio.name){//Check if portfolio with given name already exists
newPortfolio.transactions.append(newTransaction)//Add new transaction to the portfolio's transactions list
newTransaction.portfolio = newPortfolio//Link portfolio to transaction
RealmService.shared.create(newPortfolio)
RealmService.shared.create(newTransaction)
}else{
newPortfolio.transactions.append(newTransaction)
newTransaction.portfolio = newPortfolio
RealmService.shared.create(newTransaction)
}
And this is the create function:
func create<T: Object>(_ object: T){
do {
try realm.write{
realm.add(object, update: true)
}
} catch {
post(error)
}
}
I also have primaryKeys() like mentioned in documentation.
What I am doing wrong, can somebody please explain?

Answer 1

Per the Realm class description, the object has to have a primary key for the update to work. Since you didn’t mention that, I assume your realm object lacks it.
Only pass true to update if the object has a primary key. If no object exists in the Realm with the same primary key value, the object is inserted. Otherwise, the existing object is updated with any changed values.

Answer 2

Solution was that I had to get all the current ones first.
This is the logic I applied:
let currentTransactions = RealmService.shared.realm.objects(Transaction.self).filter("portfolio_name = '\(selectedPortfolioName)'")
if !RealmService.shared.ifPortfolioExists(name: newPortfolio.name){
for transaction in currentTransactions{
newPortfolio.transactions.append(transaction)
}
newPortfolio.transactions.append(newTransaction)
newTransaction.portfolio = newPortfolio
RealmService.shared.create(newPortfolio)
RealmService.shared.create(newTransaction)
}else{
for transaction in currentTransactions{
newPortfolio.transactions.append(transaction)
}
newPortfolio.transactions.append(newTransaction)
newTransaction.portfolio = newPortfolio
RealmService.shared.create(newTransaction)
}