Hi,

How can I compare two record? Like this :

Regards, Ara

aradeonas wrote

Hi, How can I compare two record?

I usually end up writing my own - as per the first answer here: http://stackoverflow.com/questions/11797069/how-to-compare-two-trect-variables-in-d7

I'd be interested in knowing if there was a more general method nowadays - though I doubt it.

Cheers

Mike
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In your example you would not need the record
if it consists of only one string component.
But you can write:

if R1.naR2.na then
    Showmessage('Error')

In general there cannot be a standard
compare function for records because
you can have a lot of different types
within a record. So you need to write
your own compare function.

At the declaration of TRec add this:

=== code begin ===

operator = (aLeft, aRight: TRec): Boolean;

=== code end ===

and then implement it like this:

=== code begin ===

operator = (aLeft, aRight: TRec): Boolean;
begin
   Result := aLeft.na = aRight.na;
end;

=== code end ===

Alternatively you can declare the operator inside TRec if you enable modeswitch advancedrecords:

=== code begin ===
type
   TRec = record
     na: String;
     class operator = (aLeft, aRight: TRec): Boolean;
   end;

=== code end ===

Implementation:

=== code begin ===

class operator TRec.=(aLeft, aRight: TRec): Boolean;
begin
   Result := aLeft,na = aRight.na;
end;

=== code end ===

This /should/ work though I did not test it by compilation.

Regards,
Sven

Thank you J?rgen,That is just a example but Its good to know there is now way.
Thank you Sven for examples.I didn't know about advanced record support.

Regards,
Ara

aradeonas wrote

operator = (aLeft, aRight: TRec): Boolean;

I get "Logical Operator not supported".

-Michael

Michael Schnell wrote

I get "Logical Operator not supported".

I do have:

{$mode objfpc}{$H+}

Michael Schnell wrote

I get "Logical Operator not supported".

I found that seemingly overloading an operator is not allowed within a procedure, while defining a type is allowed.

Is this a bug or a feature ?

Anyway, the error message is a bit misleading....

-Michael

aradeonas wrote

operator = (aLeft, aRight: TRec): Boolean;

Seemingly with "operator =", "operator " is automatically overloaded. Nonetheless it is possible to do your own (contradicting) "operator " if you like :-) .

-Michael

As Sven wrote:
"Alternatively you can declare the operator inside TRec if you enable modeswitch advancedrecords"

It means:
{$modeswitch advancedrecords}

Mattias

Mattias Gaertner wrote

"Alternatively you can declare the operator inside TRec if you enable modeswitch advancedrecords" It means: {$modeswitch advancedrecords}

Nice ! (I tested this but forgot the mode switch ;) )

Why is this mode not the default ?

-Michael