mixins: problem with variables?

[callisto]

Hi,

I have started to look at mixins. What I am aiming to do is add some implemented methods and perhaps state to a couple of otherwise independent classes. I've hit a problem, which suggests it is not possible to define local variables in a method defined in a mixin. For example:

I create one file 'main.cobra' with the code:

class TestMixin adds MyCode
    def main
        print "from main"
        .hi

and then a file 'mixin.cobra' with the code:

mixin MyCode
    def hi
        print "hi"

$ cobra mixin.cobra main.cobra

and everything is fine. (Although I went on a little detour in my current project, before realising the order of the files was significant...)

But if I modify the file 'mixin.cobra' to:

mixin MyCode
    def hi
        myvar = 0
        print "hi [myvar]"

Then I get errors on compiling:

$ cobra mixin.cobra main.cobra
main.cobra(3): error: The name "myvar" does not exist in the current context
main.cobra(4): error: The name "myvar" does not exist in the current context
Compilation failed - 2 errors, 0 warnings
Not running due to errors above.

(It is also a little confusing that the errors refer to the file holding the class which adds the mixin.)

Given the above, I've changed my program to use instance variables, but I noticed that a variable defined in a 'using' block, e.g.:

def savePdfAnalysis(filename as String, index as int)
        using document = Document()
            PdfWriter.getInstance(document, File.create(filename))
            document.open
            document.add(Paragraph("Analysis of document pair [index]"))

throws a warning:
> warning: The value of variable "document" is never used.
but the program works.

[Charles]

Mix-ins are only partially implement as described here, but I was not expecting these errors. I will take a look.

[Charles]

Fixed.

[callisto]

Charles, thanks for the quick fix. That's enough to help me move forward.

For the record, local variables still cause problems if within other blocks. e.g.

mixin MyCode
    def hi
        myvar = 0
        if myvar < 10
            inner = 2
            print "a [inner]"
        else
            print "b"

mixin.cobra(3): warning: The value of variable "myvar" is never used.
main.cobra(5): error: The name "inner" does not exist in the current context
main.cobra(6): error: The name "inner" does not exist in the current context
Compilation failed - 2 errors, 1 warning
Not running due to errors above.

[Charles]

Thanks for the report. I fixed the above case and some others. There are still some left, but you should run into this less often. I'll finish the others this week.