How to add values from one array to another?

Question

I have two arrays, from which one has to complete the other:

struct Score {
    let name: String
    let isComplete: Bool
    let finalScore: Int
}

var scores = [
    Score(name: "Steven", isComplete: false, finalScore: 12),
    Score(name: "Helen", isComplete: false, finalScore: 12),
    Score(name: "Adalbert", isComplete: false, finalScore: 12),
    Score(name: "Christian", isComplete: false, finalScore: 12),
    Score(name: "Susan", isComplete: false, finalScore: 3),
    Score(name: "Julia", isComplete: false, finalScore: 13),
    Score(name: "Robert", isComplete: false, finalScore: 13),
    Score(name: "Mercedes", isComplete: false, finalScore: 2),
    Score(name: "Gwendolin", isComplete: false, finalScore: 2),
]



struct Complete {
    let name: String
    let isComplete: Bool
}

var complete = [
    Complete(name: "Steven", isComplete: true),
    Complete(name: "Helen", isComplete: true),
    Complete(name: "Mercedes", isComplete: false),
    Complete(name: "Gwendolin", isComplete: true),
    // Name doesn´t exist in `score` and shouldn´t show up in the result:
    Complete(name: "nonexistingName", isComplete: true)
]

How could I complete the first array with the values from the second in a way that the result looks like this:

let result = [
    Score(name: "Steven", isComplete: true, finalScore: 12),
    Score(name: "Helen", isComplete: true, finalScore: 12),
    Score(name: "Adalbert", isComplete: false, finalScore: 12),
    Score(name: "Christian", isComplete: false, finalScore: 12),
    Score(name: "Susan", isComplete: false, finalScore: 3),
    Score(name: "Julia", isComplete: false, finalScore: 13),
    Score(name: "Robert", isComplete: false, finalScore: 13),
    Score(name: "Mercedes", isComplete: false, finalScore: 2),
    Score(name: "Gwendolin", isComplete: true, finalScore: 2),
]

Usually I would post a draft of my try, but since I´m quite new to swift, I have to admit I have no idea. Thanks for any advice.

A dictionary (mapping the name to the result) would be a better suited type for the scores. It allows to find and update entries efficiently. — Martin R
– Martin R, Commented Jun 26, 2017 at 21:26

GetSwifty · Accepted Answer · 2017-06-26 21:39:24Z

Ultimately you should probably re-think your models, possibly with some sort of "Player" model so you don't have this kind of disconnect.

FWIW here's a safer/simpler way to do this with a dictionary:

struct Score {
    let name: String
    var isComplete: Bool
    let finalScore: Int
}

struct Complete {
    let name: String
    let isComplete: Bool
}

var scoresDictionary: [String : Score] = [:]

// this populates scoresDictionary with your array, keyed with the names
[   Score(name: "Steven", isComplete: false, finalScore: 12),
    Score(name: "Helen", isComplete: false, finalScore: 12),
    Score(name: "Adalbert", isComplete: false, finalScore: 12),
    Score(name: "Christian", isComplete: false, finalScore: 12),
    Score(name: "Susan", isComplete: false, finalScore: 3),
    Score(name: "Julia", isComplete: false, finalScore: 13),
    Score(name: "Robert", isComplete: false, finalScore: 13),
    Score(name: "Mercedes", isComplete: false, finalScore: 2),
    Score(name: "Gwendolin", isComplete: false, finalScore: 2),
    ].forEach { scoresDictionary[$0.name] = $0}

let complete = [
    Complete(name: "Steven", isComplete: true),
    Complete(name: "Helen", isComplete: true),
    Complete(name: "Mercedes", isComplete: false),
    Complete(name: "Gwendolin", isComplete: true),
    // Name doesn´t exist in `score` and shouldn´t show up in the result:
    Complete(name: "nonexistingName", isComplete: true)
]

//Updates only the found values in scoresDictionary
complete.forEach { scoresDictionary[$0.name]?.isComplete = $0.isComplete }

// The dictionary is updated, but in case you just want the Scores, this gives you an array
let result: [Score] = Array(scoresDictionary.values)

let result: [Score] = Array(scoresDictionary.values) is getting the Score values from the dictionary and putting them in an array
Thanks a lot! I just tried with a very big Array. It´s working absolutely fine.
@ PEEJWEEJ: Would it be even better to setup the [Complete] as Dictionary as well? Like [String: Bool]?
Keep in mind these assume unique names. If that's a problem I would suggest switching to more of a database model with UIDs

paulvs · Accepted Answer · 2017-06-26 21:32:16Z

0

Basically we just iterate scores, looking for a matching Complete. If we find one, we return a Score with the attribute isComplete set true or false. If we don't find one, we return the original Score unchanged.

var final: [Score] = scores.map { aScore in

    let comp = complete.first { aScore.name == $0.name }
    if let comp = comp {
        return Score(name: aScore.name, isComplete: comp.isComplete || aScore.isComplete, finalScore: aScore.finalScore)
    }
    return aScore
}

final.forEach {
    print($0.name, $0.isComplete, $0.finalScore)
}

Prints:

Steven true 12
Helen true 12
Adalbert false 12
Christian false 12
Susan false 3
Julia false 13
Robert false 13
Mercedes false 2
Gwendolin true 2

edited Jun 26, 2017 at 21:32

answered Jun 26, 2017 at 21:20

paulvs

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6 Comments

Martin R Over a year ago

"filter + first" can be simplified using first(where:)

Josch Hazard Over a year ago

I just tried it out and it´s just awesome! Need a little time to exactly understand how it works. Thank you very much! One more question: Is this method iterating scores for every single complete value? So in this case 5 times? Because my Score array is quite big.

paulvs Over a year ago

@MartinR thanks, updated! @Josch Hazard, no, it iterates scores once, potentially iterating the whole complete array for each value in scores. So if scores is large, and complete relatively short, this should be a pretty fast solution.

GetSwifty Over a year ago

It searches complete for it's match with every item from scores. This works, but is very inefficient.

GetSwifty Over a year ago

It would actually be more efficient if the iterations were swapped

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