simple JSON work: extracting both the key and the value

Question

I have read a bit of JSON work all over the internet. as a noob, expect me to not be as good as some of you at tracking down examples, because I need knowledge to know what to search for to get knowledge. Catch22. ;-)

I'm using superobject, seems like the best way to go.

My question is, I need to separate the JSON into key/value pairs, so far I could only get value, if I know what the key is. The Key (in my app the key is the [command]) will be checked against all possible commands, and when a command matches, the value part is a comma separated list of parameters as arguments for the command that would be initiated by either side. the server/client then calls the command (a procedure/function) and passes the [commaText] as its arguments. (there may be JSON politically correct way that replaces the [commaText] and, yes, of course you may comment on that, but so far the [commaText] is a simple and easy way for me to do it.

Shorter: I need to extract both the [Key value] and the [Value value] from a JSON pair.

this is what I got working so far:

function TWebSocketServer.GetValue(const AData: String;
  Key: String): String;
var
  JSON: ISuperObject;
  rowItem: ISuperObject;
  ADataStringStream: TStringStream;
begin 
  ADataStringStream := TStringStream.Create(AData);
  JSON := TSuperObject.ParseStream(ADataStringStream, False);

  rowItem := JSON[Key];
  if Assigned(rowItem) then
    Result := rowItem.AsString
  else Result := '';
end;

this gets me the value of the pair if I already know what the key of the pair.

Restating: need to extract both key/value as separate strings from JSON data (usually/basically ever, will I have in my possession more than one key pair, its one command/ one transmission)

More background: I have a SQLDatabase/App-Server/Many Clients implementation. (App-Server I/O <-> SQL, calculates, then output to clients, clients receive the input/function call from app-server, updates it's values, and then the user may invoke a function on the App-server, through using the client to call that function -- using websockets for communication. Both app-server and clients can call functions and procedures in the api, but It'll be one command at a time from client-server or server-client.

And I have wondered if it might not be easier to create a special case JSON parser, because my data is alway only one pair, and not a big JSON object...

Please, any suggestions will be appreciated

PS. Delphi 10.1 Berlin, Windows10 x64

what library @DavidHeffernan? http://docwiki.embarcadero.com/RADStudio/Seattle/en/JSON only builds key/value pairs, it doesn't extract them. — chillum, Jul 05 '16 at 12:08
You are using superobject. Read its documentation. And FWIW the Emba library you mention does support enumeration of a JSON object — David Heffernan, Jul 05 '16 at 12:13

chillum · Answer 1 · 2016-07-06T11:50:44.467

Thanks David, all I needed :-)

This simple example shows exactly what I wanted!

procedure TfrmWebSocketServer.Button3Click(Sender: TObject);
 var
   item: TSuperAvlEntry;
   obj: ISuperObject;
 begin
  obj := SO('{"Command": "Parameters, Parameters"}');
  for item in obj.AsObject do
  begin
    vcl.Dialogs.ShowMessage(item.Name); //outputs "Command"
    vcl.Dialogs.ShowMessage(item.Value.AsString); //outputs "Parameters, Parameters"
  end;
end;

simple JSON work: extracting both the key and the value

1 Answers1