Bad excess while accessing core data Entity - core-data

Question

I am trying to fetch some record from some entity , but when trying to fetch frequently i am getting Bad Access error ,and app is crashing . please help .
var mContext:NSManagedObjectContext! = appDelegate.persistentContainer.viewContext
func getAllRoomName() -> [String] {
let fetchRequest: NSFetchRequest<SwitchMO> = SwitchMO.fetchRequest()
var arrRoomNames = [String]()
do {
if let arrSwitchesMo = try? mContext.fetch(fetchRequest) as? [SwitchMO]
{
for switchMo in arrSwitchesMo ?? []
{
arrRoomNames.append(switchMo.roomName ?? "")
}
}
} catch {
print("Error with request: \(error)")
}
arrRoomNames = Array(Set(arrRoomNames))
return arrRoomNames;
}
Bad Access Error
How can i get rid of this , Please help me .

Answer 1

If you are using a specific fetch request a type cast is redundant. And if you are using do catch don't try?
func getAllRoomName() -> [String] {
let fetchRequest: NSFetchRequest<SwitchMO> = SwitchMO.fetchRequest()
var arrRoomNames = [String]()
do {
let arrSwitchesMo = try mContext.fetch(fetchRequest)
for switchMo in arrSwitchesMo {
arrRoomNames.append(switchMo.roomName ?? "")
}
arrRoomNames = Array(Set(arrRoomNames))
} catch {
print("Error with request: \(error)")
}
return arrRoomNames
}
However you should make a function can throw if this function on its part contains a throwing function
func getAllRoomName() throws -> [String] {
let fetchRequest: NSFetchRequest<SwitchMO> = SwitchMO.fetchRequest()
var arrRoomNames = [String]()
let arrSwitchesMo = try mContext.fetch(fetchRequest)
for switchMo in arrSwitchesMo {
arrRoomNames.append(switchMo.roomName ?? "")
}
return Array(Set(arrRoomNames))
}
If the code still crashes then the managed object context is nil. Declare the context non-optional as suggested in the Core Data template.