How to check if a string contains ALL values from an String Array?

Question

Let's say I have a text and I want to check if the text contains a couple of words.

let text: String = "The rain in Spain"
let wordsA: [String] = [ "rain", "Spain" ] // should return true when compared with text
let wordsB: [String] = [ "rain", "Italy" ] // should return false when compared with text

What is the shortest, quickest way to check if my text contains ALL of the words?

I know, I can do:

var result: Bool = true
for word in wordsA {
    result = result && text.contains(word)
}

But I was wondering if there is a shorter way that involves using predicates. For instance, to check if the string contains ANY of the words I could do:

let result: Bool = wordsA.contains(where: text.contains)

Is there something similar that results only in true if ALL words are found?

@Alexander Wow that was quick, I just found it in the suggestions of my IDE, but thanks a lot! I posted it as answer. — Martin Braun
– Martin Braun, Commented May 2, 2021 at 23:19

Martin Braun · Accepted Answer · 2021-05-03 00:46:01Z

1

I found a very simple solution, which is perfect for me:

let result: Bool = wordsA.allSatisfy(text.contains)

This works, but it's not fast like Leo's solution.

edited May 3, 2021 at 0:46

answered May 2, 2021 at 23:18

Martin Braun

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Comments

Leo Dabus · Accepted Answer · 2021-05-03 00:51:51Z

1

You should enumerateSubstrings in your string using byWords option. It will return only words not a sequence of characters that might be just part of a larger word. Once you have all the words of your string you should create a set and check if it is a superset of your words. Your code should be something like:

extension StringProtocol {
    var setOfWords: Set<String> {
        var setOfWords: Set<String> = []
        enumerateSubstrings(in: startIndex..., options: .byWords) { word, _, _, _ in
            setOfWords.insert(word!)
        }
        return setOfWords
    }
}

let text = "The rain in Spain"

let wordsA = [ "rain", "Spain" ] // should return true when compared with text
let wordsB = [ "rain", "Italy" ] // should return false when compared with text

let setOfWords = text.setOfWords
setOfWords.isSuperset(of: wordsA)  // true
setOfWords.isSuperset(of: wordsB)  // false

Without extending StringProtocol:

let text = "The rain in Spain"
var setOfWords: Set<String> = []
text.enumerateSubstrings(in: text.startIndex..., options: .byWords) { word, _, _, _ in
    setOfWords.insert(word!)
}
let wordsA = [ "rain", "Spain" ]
let wordsB = [ "rain", "Italy" ]

setOfWords.isSuperset(of: wordsA)  // true
setOfWords.isSuperset(of: wordsB)  // false

edited May 3, 2021 at 0:51

answered May 3, 2021 at 0:36

Leo Dabus

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6 Comments

Martin Braun Over a year ago

I learned something new here, although it's definitely too overkill and not what I am after for my current circumstances. I will come back in the future, definitely. I'm pretty sure this will be useful to me one day.

Leo Dabus Over a year ago

@MartinBraun using a set is much faster and you don't have to search the string multiple times.

Martin Braun Over a year ago

Sounds right, but is there a way to get rid of the extension to get the thing shorter?

Leo Dabus Over a year ago

@MartinBraun sure it would be easy. Note also that your method would return true also for the string "A train in Spain"

Leo Dabus Over a year ago

@MartinBraun If you are doing a search you shouldn't use contains. You should use localizedStandardContains which is diacritic and case insensitive

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