Re: [fpc-pascal] Usage of FieldAddress
Ryan Joseph via fpc-pascal schrieb am Mo., 5. Apr. 2021, 05:58: > > > > On Apr 4, 2021, at 2:36 PM, Sven Barth via fpc-pascal < > fpc-pascal@lists.freepascal.org> wrote: > > > > The RTTI streaming relies on *published properties* (and published > methods for the event handlers). > > Sorry Sven, I'm not understand what I'm doing wrong. From original example > "scale" is a published property right? So FieldAddress only works on > published fields, which are not supported unless they are > classes/interfaces. > > type > TSomething = class(TPersistent) >private > m_scale: integer; >published > property scale: integer read m_scale write m_scale; > end; > > I have used published properties like this for JSON streaming, i.e.: > > type > TVectorObject = class(TPersistent) > private > components: array[0..2] of integer; > published > property x: integer read components[0] write components[0]; > property y: integer read components[1] write components[1]; > property z: integer read components[2] write components[2]; > end; > > which works just fine so I assume I can use the RTTI functions, just not > FieldAddress. > Correct. You need to use GetOrdProp and similar from the TypInfo unit or the object oriented variant from the Rtti unit. Note: you don't need to inherit from TPersistent if you simply want to manually access such properties, setting $M+ before the type (and resetting it afterwards) is enough to enable the published section. Regards, Sven > ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Usage of FieldAddress
> On Apr 4, 2021, at 2:36 PM, Sven Barth via fpc-pascal > wrote: > > The RTTI streaming relies on *published properties* (and published methods > for the event handlers). Sorry Sven, I'm not understand what I'm doing wrong. From original example "scale" is a published property right? So FieldAddress only works on published fields, which are not supported unless they are classes/interfaces. type TSomething = class(TPersistent) private m_scale: integer; published property scale: integer read m_scale write m_scale; end; I have used published properties like this for JSON streaming, i.e.: type TVectorObject = class(TPersistent) private components: array[0..2] of integer; published property x: integer read components[0] write components[0]; property y: integer read components[1] write components[1]; property z: integer read components[2] write components[2]; end; which works just fine so I assume I can use the RTTI functions, just not FieldAddress. Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Usage of FieldAddress
Am 04.04.2021 um 22:19 schrieb Ryan Joseph via fpc-pascal: On Apr 4, 2021, at 1:07 PM, Sven Barth via fpc-pascal wrote: Only classes or interfaces are supported as published *fields*. And the visibility of the *property* does not change the visibility of the *field*, after all the property could be provided by a method. I know FPC can deserialize JSON with TJSONDeStreamer so maybe I need to use the RTTI functions in TypInfo.pas? The RTTI streaming relies on *published properties* (and published methods for the event handlers). Regards, Sven ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Usage of FieldAddress
> On Apr 4, 2021, at 1:07 PM, Sven Barth via fpc-pascal > wrote: > > Only classes or interfaces are supported as published *fields*. > > And the visibility of the *property* does not change the visibility of the > *field*, after all the property could be provided by a method. > I know FPC can deserialize JSON with TJSONDeStreamer so maybe I need to use the RTTI functions in TypInfo.pas? Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Usage of FieldAddress
Am 04.04.2021 um 20:15 schrieb Ryan Joseph via fpc-pascal:
On Apr 4, 2021, at 12:10 PM, Sven Barth via fpc-pascal
wrote:
FieldAddress only works on published fields. Just like MethodAddress only works
on published methods.
For private fields extended RTTI is required which is not yet implemented.
I don't understand this at all I guess. I thought the properties made them published and
I get a "Symbol cannot be published, can be only a class" if I put the field
itself in the published section.
Just trying to do this:
PInteger(theClass.FieldAddress('foo'))^ := 10;
Only classes or interfaces are supported as published *fields*.
And the visibility of the *property* does not change the visibility of
the *field*, after all the property could be provided by a method.
Regards,
Sven
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Re: [fpc-pascal] Usage of FieldAddress
> On Apr 4, 2021, at 12:10 PM, Sven Barth via fpc-pascal
> wrote:
>
> FieldAddress only works on published fields. Just like MethodAddress only
> works on published methods.
>
> For private fields extended RTTI is required which is not yet implemented.
I don't understand this at all I guess. I thought the properties made them
published and I get a "Symbol cannot be published, can be only a class" if I
put the field itself in the published section.
Just trying to do this:
PInteger(theClass.FieldAddress('foo'))^ := 10;
Regards,
Ryan Joseph
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Re: [fpc-pascal] Usage of FieldAddress
Am 04.04.2021 um 19:12 schrieb Ryan Joseph via fpc-pascal: I'm trying to see fields by name but TObject.FieldAddress doesn't seem to be working. Do I have that correct I should be using FieldAddress to return the pointer of the published property? Some how I can't seem to find an example of FieldAddress on Google type TSomething = class(TPersistent) private m_scale: integer; published property scale: integer read m_scale write m_scale; end; FieldAddress only works on published fields. Just like MethodAddress only works on published methods. For private fields extended RTTI is required which is not yet implemented. Regards, Sven ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
[fpc-pascal] Usage of FieldAddress
I'm trying to see fields by name but TObject.FieldAddress doesn't seem to be working. Do I have that correct I should be using FieldAddress to return the pointer of the published property? Some how I can't seem to find an example of FieldAddress on Google type TSomething = class(TPersistent) private m_scale: integer; published property scale: integer read m_scale write m_scale; end; Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
