A question about placement of variable definitions

Unity Engine
1

In my current project i come across several situations were i need to use a variable for something in a loop.

Here theTag is defined within the loop.

foreach (GameObject aGameObject in aList) {
    string theTag = aGameObject.tag + "XXX";
    print (theTag);
}

Another similar example, with the definition of the theTag outside of the loop:

string theTag;
foreach (GameObject aGameObject in aList) {
    theTag = aGameObject.tag + "XXX";
    print (theTag);
}

My simple question is what is the correct place for “string theTag” and what is the pros&cons?

2

The overall answer is that it doesn’t really matter, and the compiler will generally optimize things like this on its own. In this particular example, there’s no real difference, because in both versions, you are creating a new string in each step of the loop anyway. In general, it’s more “correct” to define a variable that only gets used inside a loop inside that loop. If you don’t need “theTag” anywhere else further down in the code, then there’s no reason to keep it around. There might be some cases where putting it outside the loop would give a slight increase in performance, like if it was a struct (not a class) that took up a lot of memory, it’s possible you could save some small amount of performance by not having to recreate it on the stack, but like I said, I think most compilers will figure that out on their own so it almost never matters. So, in general, do it inside the loop, just because it’s one less line and one less variable hanging around lower down in the function that you don’t actually need.

3

Thanks