How to read a XMLstring from an API as a stream
lazarus / 38-Networking and Web Programming

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arneolav · 2018-03-30 21:08

From an external API I'm getting a XML file using Synapse,
Oauth1/GetBody.
The file is saved to disk (as a string,  Textfile) and then read the
diskfile:

Using TXMLConfig:
var  iDoc    : TXMLDocument;
  Child,  gChild:TDOMNode; 
...
 ReadXMLFile(iDoc,  FilePath);
      Child := iDoc.DocumentElement.FirstChild;
      while Assigned(Child) do
      begin  .....

This works great, but to avoid use of diskfile  I 'v spend some hours
to figure out how to read the input from the API as a stream.
I suppose I have to replace the "ReadXMLFile"  but can't find "how
to".
May be somebody can give me an idea.

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molly · 2018-03-30 21:44

var
  stream: Tmemorystream;
...
  stream :=Tmemorystream.create;
  // use whatever you want to fill the stream, LoadFromfile as example
  stream.LoadFromFile(FilePath)
  ReadXMLFile(iDoc,  stream);
  Child := iDoc.DocumentElement.FirstChild;
  stream.free;
  // etc.
...

See xmlread.pp:
Quoteprocedure ReadXMLFile(out ADoc: TXMLDocument; const AFilename:
String); overload;
procedure ReadXMLFile(out ADoc: TXMLDocument; var f: Text); overload;
procedure ReadXMLFile(out ADoc: TXMLDocument; f: TStream); overload;
procedure ReadXMLFile(out ADoc: TXMLDocument; f: TStream; const
ABaseURI: String); overload;

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arneolav · 2018-03-31 10:38

Hi molly!
Thanks for your insperation!
I'v been away from Lazarus som period and my head is "emty" of
"lazarus stuff".

Here is my "working" solution:

function ConvXMLstring(const XMLstr: string)          // String from
the API
var
  iDoc    : TXMLDocument;
  Child, gChild:TDOMNode;
  AStream: TStringStream;
begin
  AStream := TStringStream.Create(XMLstr);          { assign the
XMLstring to the stream}

  try
    if Assigned(AStream) then
      ReadXMLFile(iDoc, AStream);                   { read the stream,
the XMLstring }
      Child := iDoc.DocumentElement.FirstChild;     {Get first child }

  while Assigned(Child) do ....


As a help for others, here is a more complete example:

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edgarrod71 · 2018-04-24 08:50

Molly is ok, but here's another option, instead of loading it to the
Stream, we can load it directly from the TXMLDocument, and paste it to
the Stream, so we can use the stream with different controls using
only memory (so it'll be faster).

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i const
archivo='c:\where_the_file_is.xml';    [...]    if assigned(cStream)
then        FreeAndNil(cStream);       cStream :=
TStringStream.Create('', CP_UTF8);      ReadXMLFile(cDoc, archivo);  
  WriteXML(cDoc, cStream);      cStream.Seek(0, soBeginning);     
try        Memo2.Clear;        Memo2.Lines.LoadFromStream(cStream);  
  except        on EFOpenError do          ;  /// swallow the
error...      end;      cNodo := cDoc.FirstChild;     
Memo1.Lines.Clear;     
Memo1.Lines.AddText(cDoc.DocumentElement.TextContent);      [...]

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arneolav · 2018-04-24 10:32

Quote from: edgarrod71 on April 24, 2018, 10:50:13 am
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i      if
assigned(cStream) then            FreeAndNil(cStream);               
 <---  Got an error on this      if assigned(cStream) then cStream :=
nil; <---- This compile and run OK

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arneolav · 2018-04-24 10:54

I ended up with same solution as shown by edgarrod71

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i // To make
it more simple I tried to get the string direct from the API
GetBody:AStream := TStringStream.Create(Utf8ToAnsi(FConnect.GetBody));
  <-- did not work // so I have to pass the recieved string to a
function or procedure:  .....   ReadAPIstring(FConnect.GetBody);  
  function ReadAPIstring(Const XMLstring: string);  var  AStream:
TStringStream; begin    if assigned(AStream) then AStream := nil;   
AStream := TStringStream.Create(Utf8ToAnsi(XMLstring)); ......