Writing complex records to file

问题:

Hi I have defined some records in my project which may be consisted of other records and also dynamic arrays of normal data types and other records , it is n example of a record type

  Type1=record
    x:integer;
  end;
  Type2=record
    Y:array of X;
    str:string;
  end;

When I tried to save one of variables of these records type to file with blockwrite function like this :

var
  Temp1:Type2;
  begin
    setlength(temp1.y,100);
    blockwrite(MyFile,Temp1,sizeOf(Temp1);

it just wrote as much as the size of pure record is ,but temp1 has a dynmic arrays which is resized , Could someone please tell me how I can write a complex record to a file , I mean something like what is used in VB6 . Thanks

回答1:

You can use http://kblib.googlecode.com (works with any dynamic records, also records that contains other records, etc.). Tested on Delphi 2006/2009/XE (it doesn't use extended RTTI introduced in D2010). No need to write save/load code manually (just one line to save/load any dynamic type - strings, records, dynamic arrays).

In your example it would be sth. like this:

TKBDynamic.WriteTo(lStream, lType2, TypeInfo(Type2));

To load it back:

TKBDynamic.ReadFrom(lStream, lType2, TypeInfo(Type2));

If anyone is interested how to deal with 'record versions', just post new issue and then I'll write some examples.

Similar questsion:

• How Can I Save a Dynamic Array to a FileStream in Delphi?
• Delphi 2010: How to save a whole record to a file?

回答2:

This won't work. You will need to manually write (streaming) code to write every field.

Have a look at published fields/properties in classes, since together with arrays of variants, this used to be the only way to stream data using generic code.

However since D2010 the RTTI was expanded, but I don't know the exact details of that yet.