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iOS

Posted by Tom Coomer
Tom Coomer
1,331 Points

Swift While loop check Int values

I have a While loop that doesn't seem to be working. I am asking it to check one Int Value against two others but I am shown the following error message: "Type 'Int' does not conform to protocol 'BooleanType'"

Here is the loop:

            while randomIndex == itemOneNumber||itemTwoNumber {
            randomNumber()
            }

However this seems to be working

            while randomIndex == 5||7 {
            randomNumber()
            }
Manuel Schulze
Manuel Schulze
12,739 Points

Hey Tom,

I'm not so sure about it. But I think you should write the code like this:

while randomIndex == itemOneNumber || randomIndex == itemTwoNumber {
randomNumber()
}

Does this help?

Manuel Schulze
Manuel Schulze
12,739 Points

Tried my both ways in a playground and it seems that this was the problem with your code. My solution made the loop work for me.

Tom Coomer
Tom Coomer
1,331 Points

Thats perfect! Thank you

2 Answers

Tom Coomer
Tom Coomer
1,331 Points 
while randomIndex == itemOneNumber || randomIndex == itemTwoNumber {
randomNumber()
}

Thanks to Manuel Schulze

Manuel Schulze
Manuel Schulze
12,739 Points

I don't know if you understand why this has to be like this. If you do it my way it's the same as

while (randomIndex == itemOneNumber) || (randomIndex == itemTwoNumber) {...}

Your way it was like while (randomIndex == itemOneNumber) || (itemTwoNumber) {...} and the second term evaluates always as true so the loop is always running and not working properly.

I hope this helps you to understand why it has to be like I did.

Greetings

Tom Coomer
Tom Coomer
1,331 Points

Yes that is very helpful. Thank you. The thing that I couldn't work out is why it was working the second time with the integer values entered?

Manuel Schulze
Manuel Schulze
12,739 Points
Manuel Schulze
Manuel Schulze
12,739 Points

That's logical too. Swift is type safe. That means it prevents you from using an Int-Value at an "bool-spot".

Example:

var t = 1 // t gets interpreted as an Int Value. You can't do something like: if t { //your stuff }

because there has to be a conditional. So a bool value or a comparison is allowed here.

But if you do something like

if 3 { // your stuff }

the "3" will be interpreted as an Bool value and so the compiler will understand this statement as an true value. So this works.

For more information: https://developer.apple.com/library/prerelease/mac/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html

Hope I could help you.

Tom Coomer
Tom Coomer
1,331 Points

Yes that is fantastic! I understand now. Thanks again.