delphi scope of variables question

Question

i fill a tdictionary , read from a file, to iterate over the key-value-pairs. iterating was solved in delphi dictionary iterating.

the problem is that the values in the dict are not kept, probably a scope-problem with variables. i am more used to java... the values do exist directly after assigning them to the dictionary in the procedure parsetextfile, then get lost:

program parsefile;

{$APPTYPE CONSOLE}

uses
  SysUtils, Classes, StrUtils, Dialogs, Generics.collections;

var key : string;
    dict: TDictionary<String, TStringlist>;
    KeysList, Valuename: TStringList;
    KeyName: string;
    i: integer;

function DeleteSpaces(str: string): string;
var
 i: Integer;
begin
 i:=0;
while i<=Length(str) do
  if str[i]=' ' then Delete(str, i, 1)
  else Inc(i);
  Result:=str;
end;

procedure HandleOneKey(KeyIndex:Integer; PrevKeys:string);
var L:TStringList;
    i:Integer;
    Part: string;
    KeyName: string;
begin
  KeyName := KeysList[KeyIndex];
  L := dict[KeyName];
  for i:=0 to L.Count-1 do
  begin
    writeln(L[i]);
    Part := KeyName + '=' + L[i];
    if KeyIndex = (KeysList.Count-1) then
      WriteLn(PrevKeys + ' ' + Part)
    else
      HandleOneKey(KeyIndex+1, PrevKeys + ' ' + Part);
  end;
end;

procedure Split(const Delimiter: Char;Input: string;const Strings: TStrings);
begin
   Strings.Clear;
   Strings.Delimiter := Delimiter;
   Strings.DelimitedText := Input;
end;

procedure parsetestfile;
  var testfile: Textfile;
      text: string;
      splitarray: TStringList;
      subsplit1, subsplit2: TStringList;
begin
  splitarray := TStringList.Create;
  subsplit1:= TStringList.Create;
  subsplit2:= TStringList.Create;
  AssignFile(testfile, 'g:\testfile.txt') ;
  Reset(testfile);

  while not Eof(testfile) do
  begin
    ReadLn(testfile, text);
    if AnsiContainsStr(text, '=') then
    begin
      Split('=', text, splitarray);
      splitarray[0] := trim(splitarray[0]);
      splitarray[1] := DeleteSpaces(splitarray[1]);
      if AnsiStartsStr('data', splitarray[0]) then
      begin
        split(' ', splitarray[0], subsplit1);
        splitarray[0]:=subsplit1[1];
        split(',', splitarray[1], subsplit2);
        dict.Add(splitarray[0], subsplit2);
        for ValueName in dict.Values do
        begin
          for i := 0 to Valuename.Count - 1 do
          write('Values are : '+ Valuename[i]);
        writeln;
        end;//for
      end;//end-data-check
    end;//end-=-check
  end;//while
  CloseFile(testfile);
  splitarray.Free;
  subsplit1.Free;
  subsplit2.Free;
end;

begin
  dict := TDictionary<String, TStringlist>.Create;
  parsetestfile;
  KeysList := TStringList.Create;

  for KeyName in dict.Keys do
    KeysList.Add(KeyName);
  for i := 0 to Keyslist.Count - 1 do
  begin
    writeln('Keylist Items: ' + Keyslist[i]);
  end;
  if KeysList.Count > 0 then
  begin
    HandleOneKey(0, '');
  end;
  dict.Destroy;
  Keyslist.Free;
  WriteLn('Press ENTER to make the window go away');
  ReadLn;
end.

Answer 1

Top Edit

I now saw you're more used to Java, that kind of explains your problem. Java uses an Garbage Collector: if you've got a reference to something, that one thing is valid. Delphi doesn't use a GC, you're responsible for freeing all the memory you allocate. This leads to the second problem: you can free memory you're holding a reference to, there's nothing stopping you from doing that. In your parsetestfile procedure you're adding subsplit2 to the dictionary, so you're keeping a copy of that reference. Later in the same procedure you're freeing subsplit2, so your dictionary now holds a reference to what Delphi considers to be "free memory"!

With Delphi you need to be very careful and deliberate with life cycle management. In this case you obviously can't free the subsplit2 in the parsetestfile procedure itself, but you do need to free it later. You'll need to free it when you free the Dict, look at my initial code for how to do that.

*Recom

---

Here's your code with lots of things fixed. Please read the comments, I inserted comments wherever I changed something.

It compiles and values survive the parse procedure, but I'm not sure what you want to achieve and you forgot to provide a sample text file: I had to "make one up".

program Project23;

{$APPTYPE CONSOLE}

uses
  SysUtils, Classes, StrUtils, Dialogs, Generics.collections;

var deviceid, key, topmodule : string;
    dict: TDictionary<String, TStringlist>;
    KeysList: TStringList;
    KeyName: string;
    i: integer;

function DeleteSpaces(str: string): string;
var
 i: Integer;
begin
 i:=0;
while i<=Length(str) do
  if str[i]=' ' then Delete(str, i, 1)
  else Inc(i);
  Result:=str;
end;

procedure HandleOneKey(KeyIndex:Integer; PrevKeys:string);
var L:TStringList;
    i:Integer;
    Part: string;
    KeyName: string;
begin
  KeyName := KeysList[KeyIndex];
  L := dict[KeyName];
  for i:=0 to L.Count-1 do
  begin
    writeln(L[i]);
    Part := KeyName + '=' + L[i];
    if KeyIndex = (KeysList.Count-1) then
      WriteLn(PrevKeys + ' ' + Part)
    else
      HandleOneKey(KeyIndex+1, PrevKeys + ' ' + Part);
  end;
end;

procedure Split(const Delimiter: Char;Input: string;const Strings: TStrings);
begin
   Strings.Clear;
   Strings.Delimiter := Delimiter;
   Strings.DelimitedText := Input;
end;

procedure parsetestfile;
  var testfile: Textfile;
      text: string;
      splitarray: TStringList;
      subsplit1, subsplit2: TStringList;
      ValueName:TStringList; // Never Ever ignore compiler warnings!
      i: Integer; // Never Ever ignore compiler warnings!
begin
  splitarray := TStringList.Create;
  subsplit1:= TStringList.Create;      
  AssignFile(testfile, 'c:\temp\testfile.txt') ;
  Reset(testfile);

  while not Eof(testfile) do
  begin
    ReadLn(testfile, text);
    if AnsiContainsStr(text, '=') then
    begin
      Split('=', text, splitarray);
      splitarray[0] := trim(splitarray[0]);
      splitarray[1] := DeleteSpaces(splitarray[1]);
      if AnsiStartsStr('data', splitarray[0]) then
      begin

        subsplit2:= TStringList.Create; // Moved the creation of subsplit2 over here, because you need one fresh list for every line of text you read.

        split(' ', splitarray[0], subsplit1); // can't split on SPACE because the previous split allready broke the text at "=" and at SPACE. That's how DelimitedText works!
        // splitarray[0]:=subsplit1[1]; // splitarray[0] already contains the stuff before "="; And you should check the nubmer of lines in subsplit1!
        split(',', splitarray[1], subsplit2);
        dict.Add(splitarray[0], subsplit2);
        for ValueName in dict.Values do
        begin
          for i := 0 to Valuename.Count - 1 do
          writeLN('Values are : '+ Valuename[i]); // Only use Write when you intend to write the line terminator later
        writeln;
        end;//for
      end;//end-data-check
    end;//end-=-check
  end;//while
  CloseFile(testfile);
  splitarray.Free;
  subsplit1.Free;
  // subsplit2.Free; // Ooops! You're freeing Subsplit2, after you added it as a value in the dict.
end;

begin
  dict := TDictionary<String, TStringlist>.Create;
  parsetestfile;
  KeysList := TStringList.Create;

  for KeyName in dict.Keys do
    KeysList.Add(KeyName);
  for i := 0 to Keyslist.Count - 1 do
  begin
    writeln('Keylist Items: ' + Keyslist[i]);
  end;
  if KeysList.Count > 0 then
  begin
    HandleOneKey(0, '');
  end;
  dict.Free; // dict.Destroy; // never call "Destroy" directly, call .Free.
  Keyslist.Free;
  WriteLn('Press ENTER to make the window go away');
  ReadLn;
end.