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Free Pascal => General => Topic started by: soerensen3 on January 03, 2018, 01:19:47 am

Title: operator overloading and TFPGList with objects
Post by: soerensen3 on January 03, 2018, 01:19:47 am

I'm having issues using objects or records together with fpc List.
When I try to specialize a list it gives me an error (without source position) that the = operator for the record/object is not overloaded. So far, so good, even if I cannot find the line where it uses the = operator for my type in the body of TFPGList.

But even if I overload the operator it is still not working:
To compile just add the unit to the uses section of an empty program.

Code: Pascal  [Select][+][-]

1. Unit Unit1;
2. interface
3.  
4. uses
5.   fgl;
6.  
7. type
8.   { TVec2 }
9.  
10.   TVec2 = object
11.   end;
12.  
13. operator = ( A, B: TVec2 ): Boolean; //declare operator before specialization
14.  
15. type //start a new type section after operator declaration
16.   TVec2List = specialize TFPGList < TVec2 >;
17.  
18.  
19. implementation
20.  
21. operator = ( A, B: TVec2 ): Boolean;
22. begin
23.   Result:= True;
24. end;
25.  
26. end.
27.  

It can be done with records with a modeswitch and a class operator. For objects it does not work though:
http://forum.lazarus.freepascal.org/index.php/topic,36469.msg243242.html#msg243242

Is it possible to use TFGPList with objects? (I need inheritance)

Title: Re: operator overloading and TFPGList with objects
Post by: Blaazen on January 03, 2018, 01:42:31 am

See https://forum.lazarus.freepascal.org/index.php?topic=38887.0 (https://forum.lazarus.freepascal.org/index.php?topic=38887.0)

Note that you will have to switch from object to record. Also, I don't know if the directive {$MODESWITCH ADVANCEDRECORDS} is available in 3.0.2. Maybe you should upgrade to 3.0.4 or use SVN.

Title: Re: operator overloading and TFPGList with objects
Post by: soerensen3 on January 03, 2018, 01:26:44 pm

Thank you Blaazen!

I knew of the modeswitch (see the link in my post) but my question was if it was possible with objects as well, because I wanted inheritance.
But now I thought I might as well be using record helpers.

Oh and I use 3.0.4 already. The problem with the signature is you always forget updating it :)