Access to the private fields and public properties of the class

[woodhead]

Hello.
I faced the following situation: the same code is compiled in Lazarus 2.0.8 and is not compiled in Lazarus 2.0.12.

Code: Pascal  [Select][+][-]

1.   TColor = (red, green, blue);
2.  
3.   TShape = class
4.   private
5.     fColor: TColor;
6.   public
7.     property Color: TColor read fColor write fColor;
8.   end;
9.  
10.   TShapeWrapper = class
11.   private
12.     fShape: TShape;
13.   public
14.     property Color: TColor read fShape.fColor write fShape.fColor; // there is an error in this line
15.   end;

In Lazarus 2.0.12, error messages appear when trying to compile this code:

Compile Project, Target: project1.exe: Exit code 1, Errors: 2
unit1.pas(31,39) Error: Record or object type expected
unit1.pas(31,59) Error: Record or object type expected

Line 31 looks like this:

Code: Pascal  [Select][+][-]

1. property Color: TColor read fShape.fColor write fShape.fColor;

All the code is located within a same module. Please tell me how to fix it?

[lucamar]

I don't know whether it will work but, have you tried with:

Code: Pascal  [Select][+][-]

1. property Color: TColor read fShape.Color write fShape.Color;

so as to not access a private field?

If that doesn't work you'll have to use a getter/setter, I think.

[woodhead]

For this line:

Code: Pascal  [Select][+][-]

1. property Color: TColor read fShape.Color write fShape.Color;

get errors:

Compile Project, Target: project1.exe: Exit code 1, Errors: 4
unit1.pas(31,39) Error: Record or object type expected
unit1.pas(31,40) Error: Unknown record field identifier "Color"
unit1.pas(31,58) Error: Record or object type expected
unit1.pas(31,59) Error: Unknown record field identifier "Color"

I would not like to use getters/setters.

[howardpc]

I would not like to use getters/setters.

Like it or not, if you want to use properties you have to respect the syntax. The FPC loophole by which you could read/write property values by direct access to the underlying field was closed some time ago.

[woodhead]

Yep, https://wiki.lazarus.freepascal.org/User_Changes_Trunk#Property_field_access_lists_no_longer_allows_classes
Thanks

[lucamar]

Yep, https://wiki.lazarus.freepascal.org/User_Changes_Trunk#Property_field_access_lists_no_longer_allows_classes
Thanks

But that is for trunk; if you're using a normal 2.0.12 release you've got FPC 3.2.0, which shouldn't have that change ... at least it isn't mentioned in User Changes 3.2.0

[MarkMLl]

Out of curiosity: it used to be possible with Delphi to "surface" items by subclassing... does that work with FPC?

In any event, fudging something like that would probably be more work than doing it properly using properties.

MarkMLl

[Kays]

Do you really need a “wrapper”? Doesn’t inheritance

Code: Pascal  [Select][+][-]

1. TShapeWrapper = class(TShape) … end;

do the same job?

[woodhead]

But that is for trunk; if you're using a normal 2.0.12 release you've got FPC 3.2.0, which shouldn't have that change ... at least it isn't mentioned in User Changes 3.2.0

You are right. I thought so too.

Do you really need a “wrapper”? Doesn’t inheritance

Code: Pascal  [Select][+][-]

1. TShapeWrapper = class(TShape) … end;

do the same job?

This is a synthetic example to demonstrate the problem. I don't want to pile up inheritance where it can be made easier.

[PascalDragon]

Yep, https://wiki.lazarus.freepascal.org/User_Changes_Trunk#Property_field_access_lists_no_longer_allows_classes
Thanks

But that is for trunk; if you're using a normal 2.0.12 release you've got FPC 3.2.0, which shouldn't have that change ... at least it isn't mentioned in User Changes 3.2.0

Seems like it was missed to move that entry to User Changes 3.2.0, I've done so now.

I would not like to use getters/setters.

Simply do use getters and setters and declare them as inline.

[lucamar]

Seems like it was missed to move that entry to User Changes 3.2.0, I've done so now.

Thanks, Dragon. It was a little baffling to have the info as if it were for trunk but the behaviour sneaking up in the release