how to update realm object based on the certain property in Realm? - ios

Question

I have products in my Realm database like this
I want to update my realm database based on productID, so I don't need to add another product over and over again. let say I want to update quantity of product that has productID = "a" to be 5.
I have tried to write something like this.
let selectedProductID = "a"
let productsInRealmDatabase = realm.objects(Product.self)
let productIndex = productsInRealmDatabase.index(where: {$0.productID == selectedProductID})
if let productIndex = productIndex {
do {
try realm.write {
var productRealm = productsInRealmDatabase[productIndex]
productRealm.quantity = 5
productsInRealmDatabase[productIndex] = productRealm // ERROR HERE
}
} catch {
// error Handling
}
}
but I got error in : productsInRealmDatabase[productIndex] = productRealm
Error Message: Cannot assign through subscript: subscript is get-only
so how to update realm object based on the certain property in Realm?

Answer 1

You should use Realm's own filter method which accepts an NSPredicate and returns an auto-updating Results instance rather than Swift's filter when operating on Realm collections. Than either update the properties of the fetched prouduct or create a new one and save that to Realm.
let selectedProductID = "a"
let productsInRealmDatabase = realm.objects(Product.self)
let matchingProduct = productsInRealmDatabase.filter("productID == %#", selectedProductID).first
if let matchingProduct = matchingProduct {
do {
try realm.write {
matchingProduct.quantity = 5
}
} catch {
// error Handling
}
} else {
let newProduct = Product()
newProduct.productID = selectedProductID
newProduct.quantity = 5
do {
try realm.write {
realm.add(newProduct)
}
} catch {
// error Handling
}
}
If you want your Products to be unique based on their productID property, you use also set productID as the primaryKey of your Object subclass.
class Product:Object {
#objc dynamic var productID = ""
...
override static func primaryKey() -> String? {
return "productID"
}
}

Answer 2

Try this -
let selectedProductID = "a"
let productsInRealmDatabase = realm.objects(Product.self)
let filteredProducts = productsInRealmDatabase.filter("productID = \(selectedProductID)")
do {
try realm.write {
filteredProducts.forEach { product in
product.quantity = 5
}
}
} catch {
// error Handling
}

Answer 3

While inserting data to your database inside the insert function mark update key as true and then try updating the value. eg:
static func insertData() {
//Your insertion code//
try! realm.write {
realm.add(request, update: true)
}
}
static func updateData(productId: String, quantity: Int) {
let product = self.getProductData(prodId: productId)
let realm = try! Realm()
try! realm.write {
product?.quantity = quantity
}
}
Hope this helps you out.