Json Array into ListBox/Memo in Delphi xe7

Question

I'm trying to catch the following JSON array :

[{"name":"Bryan","email":"Bryan@hotmail.com"},
 {"name":"Louis","email":"Louis@hotmail.com"},
 {"name":"Maria","email":"Maria@hotmail.com"},
 {"name":"Test","email":"test@hotmail.com"},
 {"name":"Anthony","email":"anthony@hotmail.com"}]

and put it in Memo or ListBox in Delphi : the code is the following :

procedure TForm1.Button1Click(Sender: TObject);
var jv: TJSONValue;
    jo: TJSONObject;
    jp: TJSONPair;
    ja: TJSONArray;
    i: integer;
    j: integer;
begin
    RESTRequest1.Execute;

    jv:=RESTResponse1.JSONValue;


    jo:= TJSONObject.ParseJSONValue(jv.ToString) as TJSONObject;

    try
      for i := 0 to jo.Size - 1 do
      begin
        jp := jo.Get(i);
        if jp.JsonValue is TJSONArray then
        begin
            ja := jp.JsonValue as TJSONArray;
            for j := 0 to ja.Size -1 do
              Memo1.Lines.Add(ja.Get(i).ClassName + ': ' + ja.Get(j).ToString);
        end
        else
          Memo1.Lines.Add(jp.ClassName + ': '+ jp.ToString);

      end;
    finally
      jo.Free;
    end;
end;

When I click in Button I got the following error message :

Invalid class typecast

during debugging the following line has a problem : jo:= TJSONObject.ParseJSONValue(jv.ToString) as TJSONObject;

I don't know how to resolve this problem or this mistake , Could you please help me ?

Thanks.

Answer 1

I'm not sure what the problem of TJSONObject is with the string you posted.
For some reason it will parse it if you changed it.

{"Persons":[{"name":"Bryan","email":"Bryan@hotmail.com"},{"name":"Louis","email":"Louis@hotmail.com"},{"name":"Maria","email":"Maria@hotmail.com"},{"name":"Test","email":"test@hotmail.com"},{"name":"Anthony","email":"anthony@hotmail.com"}]}

If I run the code as it is I get the following result

If you don't mind using something different than default Delphi units I would suggest superobject (Link here)
superobject will parse your JSON edited and as posted.

Your code would look like this:

Const
  MyJSON = '[{"name":"Bryan","email":"Bryan@hotmail.com"},{"name":"Louis","email":"Louis@hotmail.com"},{"name":"Maria","email":"Maria@hotmail.com"},{"name":"Test","email":"test@hotmail.com"},{"name":"Anthony","email":"anthony@hotmail.com"}]';    
procedure ParseJSON;
  var
    obj: ISuperObject;
    Ar: TSuperArray;
    I: integer;
  begin
    obj := SO(MyJSON);
    if obj.IsType(stArray) then
    begin
      Ar := obj.AsArray;
      try
        for I := 0 to Ar.Length-1 do
          L.Add(Ar.O[I].AsString);
      finally
        Ar.Free;
      end;
    end
    else
      L.Add(Obj.AsString);
  end;

Result:

For Koul, to get the element names and values.
Like I said not very pretty code but ok.

Ar.O[0].AsObject.GetNames.AsArray.S[0]

To cut it up in pieces a bit.

Ar.O[0] //Get the first element in the array as ISuperObject  
.AsObject //Get it as TSuperTableString
.GetNames //Gets all names in the array, in this case "name" and "email"
.AsArray[0]//Get the first name in the names array.

It will result in email (Names are sorted A-Z)

You can do the same for the values by calling GetValues instead of GetNames.
I think the prettiest way to get it will be defining 2x more TSuperArray

procedure PrintNamesAndValues;
Var
  Ar, ArNames, ArValues:TSuperArray;
  I: Integer;
begin
  Ar := SO(<JSON string>).asArray;  
  ArNames := Ar.O[0].AsObject.GetNames.AsArray;
  ArValues := Ar.O[0].AsObject.GetValues.AsArray;
  For I := 0 to ArNames.Length-1 do
    WriteLn(Format('%s: %s',[ArNames.S[I], ArValues.S[I]]));  
end;

Hope it's all clear enough :)