SOLVED: Day 30 - Couldn't understand one specific line of code, needs some explanation – 100 Days of SwiftUI

SOLVED: Day 30 - Couldn't understand one specific line of code, needs some explanation

@banglapp

Feb '21

On Day 30, we have created a function called isOriginal(). I don't understand the statement inside the body. Actually, what I don't understand is what a logical NOT operator (!) before an array (usedWords) means. The code is as follows:

func isOriginal(word: String) -> Bool {
        !usedWords.contains(word)
}

Can anyone please explain it to me? Thank you.

@NigelGee HWS+

Feb '21

Hi @banglapp

The function pass in a String word then contains(word) see is the word is in the usedWords array would return true. The ! will return true if the word is NOT in the array.

Nigel

@ioprojecton

Feb '21

its called reverse logic or negative logic. instead of testing something to be true you are testing something to be false.

in your function it could be written like this

if contains.usedword(whatever){ return} else{ do something special }

if you need to do something only if the function doesnt return true then you can eliminate the if block and leave else block cos thats what you are interested in.

as you cant use else block by itself then you are checking whatever is in else block i.e. do something only if the function returns false.

if !function_returning_true{ do something special}

I was struggling with understanding negative logic back when i started C programming but after getting the concept i was using mostly negative logic in my code.

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