nburk nburk - 4 months ago 8
iOS Question

Realm not persisting changes made in write

I have a function where I am passing a

payment
and a
debt
object (both are structs representing the data in my Realm database). I then want to append the
payment
to the
paymentHistory
of the
debt
. Here is the code I use for this:

static func savePayment(payment: Payment, forDebt debt: Debt) throws {
let realm = try Realm()
let predicate = NSPredicate(format: "created = %@", debt.created)
guard let dbDebt = realm.objects(DBDebt.self).filter(predicate).first else { fatalError("no debt found in DB for payment") }
let dbPayment = DBPayment(payment: payment)
try realm.write {

// first try
// dbDebt.paymentHistory.append(dbPayment)

// second try
let newPaymentHistory = dbDebt.paymentHistory
newPaymentHistory?.append(dbPayment)
dbDebt.paymentHistory = newPaymentHistory
}
}


Note that I am including the code for the two attempts I've made, neither of which actually persisted the data (I checked this using the Realm Browser).

Also note that when debugging, I can see that the
DBPayment
has been created and was properly appended to the
dbDebt
's list. Maybe I am missing something obvious, but I expect this to work because in the Realm documentation, they state the following:

enter image description here

For reference, here are the definitions my structs and DB objects:

class DBDebt: Object {

dynamic var amount: Double = 0.0
dynamic var owner: DBPerson? = DBPerson()
var paymentHistory: List<DBPayment>? = List<DBPayment>()
dynamic var currency: String = Currency.Dollar.rawValue
dynamic var created: NSDate = NSDate()
dynamic var deadline: NSDate? = nil

init(debt: Debt) {
self.amount = debt.amount
self.owner = DBPerson(person: debt.owner)
self.paymentHistory = debt.paymentHistory.reduce(List<DBPayment>()) { (list: List<DBPayment>, payment: Payment) in
list.append(DBPayment(payment: payment))
return list
}
self.currency = debt.currency.rawValue
self.created = debt.created
self.deadline = debt.deadline
super.init()
}

required init(value: AnyObject, schema: RLMSchema) {
super.init(value: value, schema: schema)
}

required init(realm: RLMRealm, schema: RLMObjectSchema) {
super.init(realm: realm, schema: schema)
}

required init() {
super.init()
}

}

class DBDebt: Object {

dynamic var amount: Double = 0.0
dynamic var owner: DBPerson? = DBPerson()
var paymentHistory: List<DBPayment>? = List<DBPayment>()
dynamic var currency: String = Currency.Dollar.rawValue
dynamic var created: NSDate = NSDate()
dynamic var deadline: NSDate? = nil

init(debt: Debt) {
self.amount = debt.amount
self.owner = DBPerson(person: debt.owner)
self.paymentHistory = debt.paymentHistory.reduce(List<DBPayment>()) { (list: List<DBPayment>, payment: Payment) in
list.append(DBPayment(payment: payment))
return list
}
self.currency = debt.currency.rawValue
self.created = debt.created
self.deadline = debt.deadline
super.init()
}

required init(value: AnyObject, schema: RLMSchema) {
super.init(value: value, schema: schema)
}

required init(realm: RLMRealm, schema: RLMObjectSchema) {
super.init(realm: realm, schema: schema)
}

required init() {
super.init()
}

}


struct Payment {

init(amount: Double, paymentDate: NSDate = NSDate()) {
self.amount = amount
self.paymentDate = paymentDate
}

let amount: Double
let paymentDate: NSDate

}

class DBPayment: Object {

dynamic var amount: Double = 0.0
dynamic var paymentDate: NSDate = NSDate()

init(payment: Payment) {
self.amount = payment.amount
self.paymentDate = payment.paymentDate
super.init()
}

required init(value: AnyObject, schema: RLMSchema) {
super.init(value: value, schema: schema)
}

required init(realm: RLMRealm, schema: RLMObjectSchema) {
super.init(realm: realm, schema: schema)
}

required init() {
super.init()
}

}

Answer

In order to persist objects in realm you have to call the add() function on your realm (docs).

The following should work:

try realm.write {

  // this persists your dbPayment in your realm!
  realm.add(dbPayment)

  // first try
  // dbDebt.paymentHistory.append(dbPayment)

  // second try
  let newPaymentHistory = dbDebt.paymentHistory
  newPaymentHistory?.append(dbPayment)
  dbDebt.paymentHistory = newPaymentHistory
}
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