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

Another option which works very well for records (Delphi 2010+) is to use the SuperObject library. For example:

type
  TData = record
    str: string;
    int: Integer;
    bool: Boolean;
    flt: Double;
  end;
var
  ctx: TSuperRttiContext;
  data: TData;
  obj: ISuperObject;
  sValue : string;
begin
  ctx := TSuperRttiContext.Create;
  try
    sValue := '{str: "foo", int: 123, bool: true, flt: 1.23}';
    data := ctx.AsType<TData>(SO(sValue));
    obj := ctx.AsJson<TData>(data);
    sValue := Obj.AsJson;
  finally
    ctx.Free;
  end;
end;

I also tested this briefly with a simple TArray<Integer> dynamic array and it did not have a problem storing and loading the array elements.

In addition to the answers that indicate how you do this, please also be aware of these:

1. You must be aware that writing records out to a file will be Delphi version specific (usually: specific to a series of Delphi versions that share the same memory layout for the underlying data types).

2. You can only do that if your record does not contain fields of a managed type. Which means that fields cannot be of these managed types: strings, dynamic arrays, variants, and reference types (like pointers, procedural types, method references, interfaces or classes) and file types, or types that contain those manages types. Which basically limits to to these unmanaged types:

   • A: Simple types (including bytes, integers, floats, enumerations, chars and such)
   • B: Short strings
   • C: Sets
   • D: Static arrays of A, B, C, D and E
   • E: Records of A, B, C, D and E

In stead of writing out records to/from a file, it might be better to go with class instances and convert them to/from JSON,

If you have dynamic strings or array you can't write the record "as a whole". Instead of using old style-25 characters max strings, I would add methods to the record to be able to "stream" itself to a stream, or better using a TFiler descendant:

TMyRec = record
  A: string;
  B: Integer;
  procedure Read(AReader: TReader);
  procedure Writer(AWriter: TWriter);
end;

procedure TMyrec.Read(AReader: TReader);
begin
  A := AReader.ReadString;
  B := AReader.ReadInteger;
end;