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Ros Zunra
767 PointsHI guys, I still don't get how the postfix works
Hello everyone, here's my coding
var levelScore = 0 // 0
levelScore++ // 0
levelScore // 1
//OK, the increment appears in the next line
var totalScore = 0 // 0
/----- confusion starts -----/
totalScore = levelScore++ // 1
// Now I read this line as (totalScore) values 1 because (levelScore) values 1, the (++) hasn't worked yet.
levelScore // 2
totalScore // 1
/----- confusion ends -----/
totalScore = levelScore++ // 1
Why putting (++) in this line, when (++) only affect (levelScore) but not (totalScore)?
I can see that 1 added to the value of (levelScore) in the next line, which seems to be equal to
levelScore++ // 1
levelScore // 2
But since the value of (totalScore) won't change, what does it mean putting (++) in (totalScore = levelScore ++)?
Thank you guys!
2 Answers
Max Hirsh
16,773 PointsMy best guess is that it's one of swifts quirks/design features, so where in other programming languages you could iterate and assign to a variable in one line, but in swift you need to do it in two. I've run into this before with lengthy math formulas that I had to break into multiple steps.
Max Hirsh
16,773 PointsHey Lauren, thank you for your comment. The quirk I was talking about was not the existence of postfixes/prefixes, I was referring to how swift seems to only apply the postfixes after reading through a line of code, assigning variables and so on. If you look at the details in Ros's code example, you'll see that Swift is doing some weird things that I don't think happen in Java or most other languages that use pre/post-fixes.
Ros Zunra
767 PointsRos Zunra
767 PointsThanks!
Lauren Hibbs
1,872 PointsLauren Hibbs
1,872 PointsThis isn't a quirk of Swift. Prefix and postfix operators exist in many other programming languages.
Postfix means "after", hence "post". You first complete your operation, or pass it to a function, and then increment your variable. For example var i = 0; println(i++) // prints out 0, although the value of i is now 1
Prefix means "before" and has "pre" in it. The variable is incremented and then the operation or function is completed. var i =0; println(++i) // prints out 1, and the value of i is 1
Using prefix allows you to iterate and assign to a variable in one line. I don't have any experience in Swift, but I have a lot in Java. Hope this helps.