Re: [fpc-pascal] does Advanced Record constructor automatically zero all the memory space of that record?
On 04.10.2013 14:48, Dennis Poon wrote: You can use either FillChar as you did or use Self := Default(TTest); (default is a compiler intrinsics that returns a 0 value of the type you passed in, e.g. Nil for classes, '' for strings, 0 for ordinals and for records all fields are set to 0) How can I make it so that I only do the Self := Default() once in the parent class constructor and don't have to repeat it in all its descendant class constructor. Why would you want to do that? Classes are already zero initialized when the constructor is entered. Also using Self := Default(...) inside a class would not do what you expect it to do. Self is a class reference and thus Default(...) of the same type would return Nil and thus set your Self for the current method call to Nil (so you could no longer access the class instance at all). I noticed in your example, you have to specify the class name TTest but that implies in every descendant class, I have to replace it with the Descendant class name. Can I do self := Default(ClassType) ? hoping it will return the descendant's class type? Default expects a type identifier and nothing else. I currently don't know whether Delphi supports more. But in any way it wouldn't change much as Default(TObject) = Default(TSomeClass) = Default(TSomeChildClass) = Nil. Regards, Sven ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] does Advanced Record constructor automatically zero all the memory space of that record?
Thanks a lot for clarification. Dennis Sven Barth wrote: On 04.10.2013 14:48, Dennis Poon wrote: You can use either FillChar as you did or use Self := Default(TTest); (default is a compiler intrinsics that returns a 0 value of the type you passed in, e.g. Nil for classes, '' for strings, 0 for ordinals and for records all fields are set to 0) How can I make it so that I only do the Self := Default() once in the parent class constructor and don't have to repeat it in all its descendant class constructor. Why would you want to do that? Classes are already zero initialized when the constructor is entered. Also using Self := Default(...) inside a class would not do what you expect it to do. Self is a class reference and thus Default(...) of the same type would return Nil and thus set your Self for the current method call to Nil (so you could no longer access the class instance at all). I noticed in your example, you have to specify the class name TTest but that implies in every descendant class, I have to replace it with the Descendant class name. Can I do self := Default(ClassType) ? hoping it will return the descendant's class type? Default expects a type identifier and nothing else. I currently don't know whether Delphi supports more. But in any way it wouldn't change much as Default(TObject) = Default(TSomeClass) = Default(TSomeChildClass) = Nil. Regards, Sven ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal - No virus found in this message. Checked by AVG - www.avg.com Version: 2013.0.3408 / Virus Database: 3222/6723 - Release Date: 10/04/13 ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] does Advanced Record constructor automatically zero all the memory space of that record?
If in doubt, why not to use the old-school records and an init-value procedure. thanks, Dmitry On Tuesday, September 24, 2013, Dennis Poon wrote: ** if not, is there a clean and easy way to initialize the entire record memory space to zeros e.g. constructor TMyRecord.Create(TheValue : Integer); begin FillChar(self, sizeof(Self), 0); Value := TheVal; end; Is there a Self variable for advanced record methods/constructors ? By the way, is there an ultimate inherited constructor Create for all advanced record types? I cannot find any info by googling, so had to ask for your help here. Thanks in advanced. Dennis ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] does Advanced Record constructor automatically zero all the memory space of that record?
does Advanced Record constructor automatically zero all the memory space of that record? No, it does not. Neither in Delphi nor in FPC. Am 24.09.2013 12:36, schrieb Dennis Poon: if not, is there a clean and easy way to initialize the entire record memory space to zeros e.g. constructor TMyRecord.Create(TheValue : Integer); begin FillChar(self, sizeof(Self), 0); Value := TheVal; end; You can use either FillChar as you did or use Self := Default(TTest); (default is a compiler intrinsics that returns a 0 value of the type you passed in, e.g. Nil for classes, '' for strings, 0 for ordinals and for records all fields are set to 0) Is there a Self variable for advanced record methods/constructors ? Yes. By the way, is there an ultimate inherited constructor Create for all advanced record types? No. Regards, Sven ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] does Advanced Record constructor automatically zero all the memory space of that record?
Sven Barth wrote: does Advanced Record constructor automatically zero all the memory space of that record? No, it does not. Neither in Delphi nor in FPC. Am 24.09.2013 12:36, schrieb Dennis Poon: if not, is there a clean and easy way to initialize the entire record memory space to zeros e.g. constructor TMyRecord.Create(TheValue : Integer); begin FillChar(self, sizeof(Self), 0); Value := TheVal; end; You can use either FillChar as you did or use Self := Default(TTest); (default is a compiler intrinsics that returns a 0 value of the type you passed in, e.g. Nil for classes, '' for strings, 0 for ordinals and for records all fields are set to 0) Is there a Self variable for advanced record methods/constructors ? Yes. By the way, is there an ultimate inherited constructor Create for all advanced record types? No. Regards, Sven Thanks for your help. Are the above info. available anywhere in FPC's web site that I overlooked? If not, maybe it should be added to its wiki. Dennis ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] does Advanced Record constructor automatically zero all the memory space of that record?
Am 24.09.2013 16:40, schrieb Dennis Poon: Sven Barth wrote: does Advanced Record constructor automatically zero all the memory space of that record? No, it does not. Neither in Delphi nor in FPC. Am 24.09.2013 12:36, schrieb Dennis Poon: if not, is there a clean and easy way to initialize the entire record memory space to zeros e.g. constructor TMyRecord.Create(TheValue : Integer); begin FillChar(self, sizeof(Self), 0); Value := TheVal; end; You can use either FillChar as you did or use Self := Default(TTest); (default is a compiler intrinsics that returns a 0 value of the type you passed in, e.g. Nil for classes, '' for strings, 0 for ordinals and for records all fields are set to 0) Is there a Self variable for advanced record methods/constructors ? Yes. By the way, is there an ultimate inherited constructor Create for all advanced record types? No. Regards, Sven Thanks for your help. Are the above info. available anywhere in FPC's web site that I overlooked? If not, maybe it should be added to its wiki. Both points should be added to the documentation, but since they both are implemented only in trunk this is not the case yet. Default() is also mentioned here: http://wiki.lazarus.freepascal.org/FPC_New_Features_Trunk#New_compiler_intrinsic_Default Regards, Sven ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
