Is there a way to break from processing a list via .each? Using a return from the closure (obviously) moves on to the next item.

I could do a for loop instead but that's not as tidy and leaves me open to index errors.

Am I missing an elegant alternative (like Java's "for (a: b)") that you can break from?

sys::List.eachWhile method does what you want, and does the right thing so it can be nested!

Or you could use List.find() also. They're both pretty simliar if you're not going to use the return value.

[1, 2, 3].find |Int int -> Bool| {
  ...
  if (int == 2)
    return true
  ...
  return false
}

[1, 2, 3].eachWhile |Int int -> Bool?| {
  ...
  if (int == 2)
    return true // return anything that's not null
  ...
  return null
}

Thanks, guys.

I couldn't get it working exactly as per your examples - the compiler was complaining about returns in it-blocks - (I must still be missing some language fundamentals at the moment, but of course I'd rather try to get things working rather than read the manual!). I have managed to do it using eachWhile, but it was a little messier than your code:

rows.eachWhile |Row row -> Bool?| {

so that it would accept null/non-null returns and not complain about the it-block.

Yep, that's right. I missed that bit off - oops!

By convention, we'd typically write something like this:

rows.eachWhile |row|
{
  if (my row) return non-null result
  return null
}

Brian,

That was part of my problem. It is of course possible (likely!) that I've structured my code badly, but removing the return Type i.e. making

|Row row -> Bool?|

into

|Row row|

gives me a compiler error:

Cannot return a value from Void method