Jonas Maebe wrote:
On 27 Nov 2009, at 15:49, Juha Manninen wrote:
If I define a private integer:
TDemo = class(TCustomApplication)
private
i: integer;
...
and in a protected method I use it:
for i := 0 to List.Count - 1 do
...
then I get an error:
Error: Illegal counter variable
Moving it to method's var section helps.
Method's var section is also better place for it in general, but still it
should be legal to use a private member as counter var.
The reason is that a for-loop tries to make a number of reasonable
guarantees that the counter variable cannot be modified during the loop.
E.g., direct assignments to a counter variable are forbidden inside the
loop (except in TP-mode). If you use a private field, then any method of
that class called in the body of the loop can easily (accidentally)
change the value of the counter variable, completely messing up the loop.
In any case, why would one want a loop counter to have any more than the
minimum possible scope? Why would one want it to be a class data member
at all? Surely it would be far better/neater/more elegant, if it is used
by methods, to pass it as a parameter?
FP
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