Kurt Wrote:
>>But you are relying on a side-effect of calling the function, which is
a sneaky way of
>>introducing errors. ie:
>> x := 127;
>> // there is an item with status = ON?
>> if FindFirstMatch(List, ON, x) then
>> item := something
>> else
>> item := List[x];
>> // Now what is the status of item?
I think this may be taking the usage out of context a little. There is
nothing sneaky about misusing an answer of true or false to define if an
item is found. It is a lot more sneaky to use -1 as a false answer
because array and property indexes can happily use negative values. Ie
Array[-10..10] of TObject
This is one appropriate usage and example of a boolean function
returning true or false
If FindFirstMatch(Alist,Astatus,AitemIndex { or AITem}) then
Begin
//Do something with Alist[AItemIndex]
// >> if this was Aitem instead of itemindex then do something with
AItem
End else
Begin
//Handle Exception for nothing in list without status matching.
End;
If there was no match then you don't write Code that GV's on invalid
indexing.
>> x := FindFirstMatch (List, OFF);
>> item := List[x]; // Bang! there is no item List[-1]!
This is just bad programming that the boolean result stops from
happening in the same fashion as
x := FindFirstMatch (List, OFF);
if x <> -1 then
item := List[x] else
item := nil ;
They all do the same thing except with the second option, you still have
to check for
if assigned(Item) then
begin
//do something
end else
begin
// do something when no match.
end;
the boolean function option is the only method that prevents you from
having to then provide multiple boolean tests following the execution of
the procedure.
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