Sum the Values of Nested Custom Objects in Swift - swift

Question

I am trying to add up the values found within some custom objects in Swift. I have the follow code working in a Playground:
//Custom Object
class EntryPack: NSObject{
var date: String!
var duration: Double!
var customValues:[CustomValuePack] = [] //Nested array of objects declared below
}
//Another object to nest in the above
class CustomValuePack: NSObject{
var name:String!
var value: Double!
}
//Instantiate nested objects
let cv1 = CustomValuePack()
cv1.name = "Day"
cv1.value = 1.2
let cv2 = CustomValuePack()
cv2.name = "Day"
cv2.value = 1.3
let cv3 = CustomValuePack()
cv2.name = "Night"
cv2.value = 2.2
//Instantiate parent objects
let entry1 = EntryPack()
entry1.date = "bingo"
entry1.duration = 1.1
entry1.customValues = [cv1, cv2]
let entry2 = EntryPack()
entry2.date = "bingo"
entry2.duration = 2.2
let entry3 = EntryPack()
entry3.date = "dang"
entry3.duration = 3.0
//Throw it all together into an array
var package = [entry1, entry2, entry3]
//Predicate for some filtering
let predicate = NSPredicate(format:"date = %#", "bingo")
let results = (package as NSArray).filteredArrayUsingPredicate(predicate) as! [EntryPack]
//Sum all the parent object durations
let sum = results.reduce(0.0) { $0 + $1.duration }
print(sum) // = 3.3
But now I want to add up the value for each CustomValuePack where the name is "Day".
I can't figure out how to do a similar reduce on a nested array of objects. I've tried something like this, but it yields a syntax error:
let sum2 = results.reduce(0.0) { $0.customValues + $1.customValues.value } //Error
How do I sum the value in a nested array of objects? I eventually want to apply an NSPredicate to filter by name = Day as well, but I'm not that far yet.

Answer 1

Given entries defined as follow
let entries = [entry1, entry2, entry3]
you can extract the CustomValues with name == "Day" and sum the value field with this code
let sum = entries
.flatMap { $0.customValues }
.filter { $0.name == "Day" }
.map { $0.value }
.reduce(0, combine: +)
Improvements
You are using Swift but for some reason there still is a lot of Objective-C into your code.
This is how i would refactor your code
struct EntryPack {
let date: String
let duration: Double
let customValues:[CustomValuePack]
}
struct CustomValuePack {
let name:String
let value: Double
}
let cv1 = CustomValuePack(name: "Day", value: 1.2)
let cv2 = CustomValuePack(name: "Day", value: 1.3)
let cv3 = CustomValuePack(name: "Night", value: 2.2)
let entry1 = EntryPack(date: "bingo", duration: 1.1, customValues: [cv1, cv2])
let entry2 = EntryPack(date: "bingo", duration: 2.2, customValues: [])
let entry3 = EntryPack(date: "dang", duration: 3.0, customValues: [])
Please note that now EntryPack and CustomValuePack are structs which are value types.