CODEWITHSUNDEEP
swiftdictionarysum
Lukas_T
Lukas_T

Reputation: 299

How can a sum multiple values from the same key across different dictionaries in swift?

I am new to Swift and iOS dev. in general. I was wondering how I could sum multiple values from the same key across different dictionaries. e.g. I have

20 dictionaries with the same key value pair [String: AnyObject] e.g. "Height": 20 I want to sum these and calculate the average. EG:

// Example dictionary 
let player17: [String: AnyObject] = [
    "Name": "Les Clay",
    "Height": 42,
    "Soccer Experience": true,
    "Guardian Name(s)": "Wynonna Brown"
]

//Used any object here as they all go into a big array

Upvotes: 0

Views: 825

Answers (2)

Luca Angeletti
Luca Angeletti

Reputation: 59526

Given

let players: [[String:AnyObject]] = ...

here's another approach 

let sum = players.flatMap { $0["Height"] as? Int }.reduce(0, combine: +)

If a dictionary doesn't have a valid Int value for the "Height" key then that dictionary is ignored.

Upvotes: 1

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726839

You can use reduce to add numbers up, like this:

let totalHeight = allPlayers.reduce(0) { (p, c) -> Int in
    return p + (c["Height"] as! Int)
}

Note: The c["Height"] as! Int approach requires hard knowledge that "Height" key is present in every dictionary, and its value is of type Int. Otherwise, this will produce an exception at run time.

If some of your dictionaries do not have the proper key in them, or contain the value of a different type, you need to pre-filter or use an optional cast, for example

return p + ((c["Height"] as? Int) ?? 0)

Upvotes: 1

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