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Convert object properties to delimited string and save results to file

Suppose we have a Customer obj with the following properties:
- Id
- Name
- Address

I would like to Convert object properties to delimited string with a object method like:

function Customer.ToString(const aDelimiter: Char): string;
begin
  //SAmple code for csv, need change to use aDelimiter parameter
  Result := Format("%s,%s,%s",Id, Name, Description);
end;

where aDelimiter can be ",", ";", tab(\t), etc.

Notice that the result string will be stored in a stringlist later on to be output to a file. For example the Pseudo code:
csvList := TStringList.Create;
foreach customer in CustomerList
  csvList.Add(customer.ToString(',');
csvList.SaveToFile("CustomerExport.csv");

There are thousands of lines to store from CustomerList, any ideas on how to make it this export more efficient will be greatly appreciated.
Note: Compiler is still Delphi 7.
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Miguel Oz
Asked:
Miguel Oz
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2 Solutions
 
Ephraim WangoyaCommented:

I dont think you can get alot more efficiency out of a sequential list. You have to iterate all the objects in any case.
However you can eliminate the saving to stringlist, save it straight to a file, this will be much faster

You could make the object much better by adding the save method to the CustomerList object and let the methods of the List handle the iteration and also set the delimiter once in the CustomerList Object

private
   FDelimiter: Char;
   function GetText: string;
public
    procedure SaveToFile(const AFileName: string);
    .....
    property Delimiter: char read FDelimiter write FDelimiter;
end;





function TCustomerList.GetText;
var
  L, Size, Count: Integer;
  P: PChar;
  S, LB: string;
begin
  Count := GetCount;
  Size := 0;
  LB := #13#10;
  foreach customer in CustomerList
    Inc(Size, Length(Customer.ToString(FDelimiter) + Length(LB));

  SetString(Result, nil, Size);
  P := Pointer(Result);
  foreach customer in CustomerList
  begin
    S := Customer.ToString(FDelimiter;
    L := Length(S);
    if L <> 0 then
    begin
      System.Move(Pointer(S)^, P^, L);
      Inc(P, L);
    end;
    L := Length(LB);
    if L <> 0 then
    begin
      System.Move(Pointer(LB)^, P^, L);
      Inc(P, L);
    end;
  end;
end;


procedure TCustomerList.SaveToFile(const AFileName: string);
var
  Stream: TFileStream;
  S: string;
begin
  Stream := TFileStream.Create;
  try
    S := GetText;
    Stream.WriteBuffer(Pointer(S)^, Length(S));
  finally
    FreeAndNil(Stream);
  end; 
end;

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Miguel OzSoftware EngineerAuthor Commented:
Your code does not implement Customer.ToString method using the delimiter parameter.
If you can add thta to your answer will be great
Thanks.
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Ephraim WangoyaCommented:

Since Delimiter is already a property of the CustomerList and is accessed within the method GetText, you just set and call SaveToFile


  CustomerList.Delimiter := ',';
  CustomerList.SaveToFile('c:\CusomerExport.csv');
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Miguel OzSoftware EngineerAuthor Commented:
The delimiter is only for the customer properties.
Your posted code use this construct:
Customer.ToString(FDelimiter)
but the implementation (ToString method at Customer object) is not posted. The main objective of this question is how to convert the object to string taking in consideration that this string will be later used in a big list to save it to a file.
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Ephraim WangoyaCommented:



function Cusomer.ToString(const ADelimiter: string): string;
begin
  Result := Format('%d%s%s%s%s',
      [Id, FDelimiter, Name, FDelimiter, Description]);
end;
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SAMIR BHOGAYTAFreelancer and IT ConsultantCommented:
Hi, this is very useful to you the code is very large so i will give you a link for that

http://www.dotnetperls.com/convert-dictionary-string

http://www.switchonthecode.com/tutorials/csharp-tutorial-serialize-objects-to-a-file
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epasquierCommented:
You can use a TStringList to build your delimited string. It requires a delimiter, and also a quote in case there can be occurences of the delimiter in the values (the address might contain coma, for example)
the resulting string could then be :

1;John Smith;"123, main street road"
function TCustomer.ToString(Delim:Char=',';Quote:Char='"'):String;
Var
 L:TStringList;
begin
 L:=TStringList.Create;
 L.Delimiter:=Delim;
 L.QuoteChar:=Quote;
 L.Add(IntToStr(ID));
 L.Add(Name);
 L.Add(Address);
 Result:=L.DelimitedText;
 L.Free;
end;

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Miguel OzSoftware EngineerAuthor Commented:
I use this method:
function Customer.ToString(const AFormat: string): string;
begin
  Result := Format(AFormat,  [Id, Name, Description]);
end;
where  AFormat = '%s,%s,%s'; or any other delimiter I need.Thus the formatiing string is build once and use multiple times

Thank you all for your comments. I will keep the question open a bit longer to see if there is any faster way to do this.
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epasquierCommented:
You can't get it faster.
Not that it matters anyway, you won't see much difference, even if you use the stringlist Delimited text functionality.
You probably should choose the method to use by considering the ease of coding and maintaining more the speed of execution, as your probable bottleneck is the writing of the file, not the generation of each line. For example, saving each line in a text file line by line instead of all in one SaveToFile will be quicker and consume less memory in the process.
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Miguel OzSoftware EngineerAuthor Commented:
Guideline without profile backing
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