Delphi 2010: How to save a whole record to a file?

Question

I have defined a record which has lots of fields with different types (integer, real , string, ... plus dynamic arrays in terms of "array of ..."). I want to save it as a whole to a file and then be able to load it back to my program. I don't want to go through saving each field's value individually. The file type (binary or ascii or ...) is not important as long Delphi could read it back to a record.

Do you have any suggestions?

Answer 1

You can load and save the memory of a record directly to and from a stream, as long as you don't use dynamic arrays. So if you use strings, you need to make them fixed:

type TTestRecord = record 
  FMyString : string[20]; 
end; 

var 
  rTestRecord: TTestRecord;
  strm : TMemoryStream; 

strm.Write(rTestRecord, Sizeof(TTestRecord) );

You can even load or save an array of record at once!

type TRecordArray = array of TTestRecord;

var ra : TRecordArray; 

strm.Write(ra[0], SizeOf(TTestRecord) * Length(ra));

In case you want to write dynamic content:

iCount   := Length(aArray);
strm.Write(iCount, Sizeof(iCount) );      //first write our length
strm.Write(aArray[0], SizeOf * iCount);   //then write content

After that, you can read it back:

strm.Read(iCount, Sizeof(iCount) );       //first read the length
SetLength(aArray, iCount);                //then alloc mem
strm.Read(aArray[0], SizeOf * iCount);    //then read content