Pascal (Lazarus/Delphi)

Firebase GET - Reading Data

See more Firebase Examples

Demonstrates how to read parts of a Firebase JSON database. The data used in this example is at Chilkat Firebase Pigs Database, and is shown here:

Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.FileAccess,
  Chilkat.Rest,
  Chilkat.AuthGoogle,
  Chilkat.StringBuilder,
  Chilkat.JsonObject;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  fac: TFileAccess;
  accessToken: string;
  rest: TRest;
  authGoogle: TAuthGoogle;
  jsonResponse: string;
  piggyPath: TStringBuilder;
  shallow: TJsonObject;
  piggyData: TJsonObject;
  count: Integer;
  i: Integer;
  piggyJson: string;

begin
  success := False;

  //  Demonstrates how to read parts of a Firebase JSON database.

  //  This example requires the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  //  This example assumes a JWT authentication token, if required, has been previously obtained.
  //  See Get Firebase Access Token from JSON Service Account Private Key for sample code.

  //  Load the previously obtained Firebase access token into a string.
  fac := TFileAccess.Create;
  accessToken := fac.ReadEntireTextFile('qa_data/tokens/firebaseToken.txt','utf-8');
  if (fac.LastMethodSuccess <> True) then
    begin
      WriteLn(fac.LastErrorText);
      Exit;
    end;

  rest := TRest.Create;

  //  Make the initial connection (without sending a request yet).
  //  Once connected, any number of requests may be sent.  It is not necessary to explicitly
  //  call Connect before each request.  
  success := rest.Connect('chilkat.firebaseio.com',443,True,True);
  if (success <> True) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;
  //  If authentication is required...
  authGoogle := TAuthGoogle.Create;
  authGoogle.AccessToken := accessToken;
  rest.SetAuthGoogle(authGoogle);

  //  Chilkat's sample data (pig-rescue data) is publicly readable at: https://chilkat.firebaseio.com/.json

  //  Let's get the animals with the shallow parameter so we can see how many pigs exist.
  jsonResponse := rest.FullRequestNoBody('GET','/pig-rescue/animal.json?shallow=true');
  if (rest.LastMethodSuccess <> True) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  //  The JSON returned should look like this:  
  //  {"-KI3bD-FU_Dake7sYOiP":true,"-KI3bD-FU_Dake7sYOiT":true,"-KI3bD-FU_Dake7sYOiS":true,"-KI3bD-FU_Dake7sYOiU":true,"-KI3bD-FU_Dake7sYOiV":true,"-KI3bD-FU_Dake7sYOiR":true,"-KI3bD-FU_Dake7sYOiQ":true}
  WriteLn(jsonResponse);

  //  Parse the response so we can iterate over each pig in the database..
  piggyPath := TStringBuilder.Create;
  shallow := TJsonObject.Create;
  piggyData := TJsonObject.Create;
  shallow.Load(jsonResponse);
  count := shallow.Size;
  i := 0;
  while i < count do
    begin

      //  Get each individual pig's data.
      piggyPath.Clear();
      piggyPath.Append('/pig-rescue/animal/');
      piggyPath.Append(shallow.NameAt(i));
      piggyPath.Append('/.json');

      piggyJson := rest.FullRequestNoBody('GET',piggyPath.GetAsString());
      if (rest.LastMethodSuccess <> True) then
        begin
          WriteLn(rest.LastErrorText);
          Exit;
        end;

      //  Show this piggy's data...
      //  An example of one pig's data is shown here:
      //  {"birth":"February, 1998","from":"Middle Ave.","gender":"F","in-date":"January, 2000",
      //    "name":"Molly II","picture":{"caption":"Molly in the Pasture","description":"Black pig","file":"molly_th.jpg"},
      //    "species":"pot belly pig","type":"Cathy's Herd"}
      WriteLn('---- ' + i + ' ----');
      WriteLn(piggyJson);

      //  Let's get the pig's name, and the caption of the picture.
      piggyData.Load(piggyJson);
      WriteLn('name: ' + piggyData.StringOf('name'));
      WriteLn('caption: ' + piggyData.StringOf('picture.caption'));

      i := i + 1;
    end;

  //  Note: In many of the Chilkat examples, you may notice strange ways
  //  of doing something that should be simpler and shorter.  For example,
  //  building the piggyPath (above) could've been written differently,
  //  with some simple string concatenation.
  //  
  //  The reason is that the Chilkat examples are written in a 
  //  proprietary "example code" scripting language,
  //  and then automatically generated to each of the different programming
  //  languages you see on example-code.com.  The code generation is
  //  limited in what it can do.  For example, string concatentation
  //  is not yet a feature of the "example code" scripting language (as of May 2016), 
  //  and therefore you won't see the use of a programming language's string
  //  concatentation operators in any example.  
  //  


  fac.Free;
  rest.Free;
  authGoogle.Free;
  piggyPath.Free;
  shallow.Free;
  piggyData.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.