class variables and static fields
lazarus / 62-General

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Zoran · 2014-02-21 14:59

Since FPC 2.6 class fields can be declared this way (as documented in
this wiki page):
Code: [Select]type
  TSomeClass = class
  public
    class var
      FSomeClassVar: TSomeType;
  end;

In this example variable FSomeClassVar is allocated globally (just one
variable exists per class, not per class instance), and it can be
accessed through class name (TSomeClass.FSomeClassVar).

In fpc documentation, I didn't find anything about these class
variables.

However, in Reference guide, I found about static fields. Although
Reference guide mentions these in chapter about old tp style objects,
I tried and this syntax works in classes.

My question is - are there any differences between these two? Are
these static fields and class vars actually same thing?

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Leledumbo · 2014-02-21 22:58

Quoteare there any differences between these two? Are these static
fields and class vars actually same thing?http://docwiki.embarcadero.c
om/RADStudio/XE5/en/Methods#Class_Static_Methods

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Zoran · 2014-02-21 23:34

Quote from: Leledumbo on February 21, 2014, 11:58:22 pmQuoteare there
any differences between these two? Are these static fields and class
vars actually same thing?http://docwiki.embarcadero.com/RADStudio/XE5/
en/Methods#Class_Static_Methods

Thanks, Leledumbo, for trying to help, but this link says nothing
about what I asked. It doesn't even talk about fields, but about
methods.
However, starting from your link, I jumped to the article about
fields, where class fields in Delphi are mentioned. Still, there is
nothing about static fields, so my question is still without answer.

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engkin · 2014-02-22 01:36

Quote from: Zoran on February 21, 2014, 03:59:04 pmMy question is -
... Are these static fields and class vars actually same thing?
Yes. Based on a comment in the source code, class var is a section
where all fields inside it are static, while static directive is used
for one single field.

Quote from: compiler\pdecvar.pas    procedure
read_record_fields(options:Tvar_dec_options; reorderlist:
TFPObjectList; variantdesc : ppvariantrecdesc);
...
                 { if it is not a class var section and token=STATIC
then it is a class field too }

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Zoran · 2014-02-26 07:51

Thank you, so these are same.

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BigChimp · 2014-02-26 09:00

@Zoran/anyone: please feel free to raise a bug against
documentation/fpdoc on the bugtracker pointing out the missing
documentation. Doc bugs are almost always resolved, though it may take
some time...

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Zoran · 2014-02-26 10:35

Quote from: BigChimp on February 26, 2014, 10:00:12 am@Zoran/anyone:
please feel free to raise a bug against documentation/fpdoc on the
bugtracker pointing out the missing documentation. Doc bugs are almost
always resolved, though it may take some time...

Okay, here it is: http://bugs.freepascal.org/view.php?id=25786

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BigChimp · 2014-02-26 10:51

Thanks a lot!