Re: pattern in for loop

Sorry, I missed the end... :)

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Ronald Steinhau wrote:

I have a model with a class "DFeature" and two inheriting classes
"DAttr" and "DRef" of feature. Furthermore a class "DClass" with an
association 1:N to features. Now i want to use patterns in for loops, like

for (attr:DAttr <- cls.getFeatures) ...

with cls being of type "DClass", but scala won't compile. I hoped, that
"attr:DAttr" would be treated as a pattern with a variable and a class
type (like in regular type pattern matches) and would only yield the
proper elements of the list. I know, that the condition "if
(attr.isInstanceOf[DAttr])" in the for part would do it, too, but it is
longer and I need a cast to DAttr afterwards, too. Is there a reason,
that this pattern is not recognized/allowed here? Am I missing something?
Ronald Steinhau

"val" has been deprecated in for comprehensions, I think. Not the concept, just using the keyword.

On Fri, Jul 31, 2009 at 1:17 AM, Naftoli Gugenheim <naftoligug@gmail.com> wrote:

Use multiple parts to the for.
for(x <- xs;
 if x.isInstanceOf[Y];
 val y = x.asInstanceOf...

-------------------------------------
Ronald Steinhau<st@entimo.de> wrote:

I have a model with a class "DFeature" and two inheriting classes
"DAttr" and "DRef" of feature. Furthermore a class "DClass" with an
association 1:N to features. Now i want to use patterns in for loops, like

for (attr:DAttr <- cls.getFeatures) ...

with cls being of type "DClass", but scala won't compile. I hoped, that
"attr:DAttr" would be treated as a pattern with a variable and a class
type (like in regular type pattern matches) and would only yield the
proper elements of the list. I know, that the condition "if
(attr.isInstanceOf[DAttr])" in the for part would do it, too, but it is
longer and I need a cast to DAttr afterwards, too. Is there a reason,
that this pattern is not recognized/allowed here? Am I missing something?
Ronald Steinhau

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