Delphi: Accessing JSON Objects within a JSON Array

Question

I have a JSON Object, let\'s name it jObject that looks like this:

{
  \"id\": 0,
  \"data\": \"[{DAT_INCL: \\\"08/03/2012 10:07:08\\\", NUM_ORDE: 1, NUM_ATN         


        

Answer 1

If you have an array from DBXJSON, then it is a TJSONArray. Call its Get method to get an element of the array.

var
  Value: TJSONValue;

Value := jArray.Get(0);

You can also go through the entire array with a for loop:

for Value in jArray do

---

But if you check the Size property and get 6226004 instead of 3, that suggests there's something else wrong here. My guess is that what you think is a TJSONArray isn't really that type. Use as to do a checked type cast:

jArray := jPair.JsonValue as TJSONArray;

You'll get an EInvalidCast exception if that fails.

Answer 2

here is an sample code to parse and output your json data. I've modified your JSON data and added ArrayData field, wich contains your initial array of objects:

program Project1;
{$APPTYPE CONSOLE}
{$R *.res}

uses
  System.SysUtils, dbxjson;

const JSON_DATA = '{"ArrayData":['+
                    '{"DAT_INCL":"07/03/2012 17:33:03", "NUM_ORDE":1,"NUM_ATND":1, "NUM_ACAO":2, "NUM_RESU":3},'+
                    '{"DAT_INCL":"07/03/2012 17:33:05", "NUM_ORDE":2,"NUM_ATND":1, "NUM_ACAO":4, "NUM_RESU":5},'+
                    '{"DAT_INCL":"07/03/2012 17:33:05", "NUM_ORDE":3,"NUM_ATND":1, "NUM_ACAO":8, "NUM_RESU":null}'+
                   ']}';


var jsv   : TJsonValue;
    originalObject : TJsonObject;

    jsPair : TJsonPair;
    jsArr : TJsonArray;
    jso  : TJsonObject;
    i : integer;
begin
    try
        //parse json string
        jsv := TJSONObject.ParseJSONValue(JSON_DATA);
        try
            //value as object
            originalObject := jsv as TJsonObject;

            //get pair, wich contains Array of objects
            jspair := originalObject.Get('ArrayData');
            //pair value as array
            jsArr := jsPair.jsonValue as  TJsonArray;

            writeln('array size: ', jsArr.Size);
            //enumerate objects in array
            for i := 0 to jsArr.Size - 1 do begin
                writeln('element ', i);
                // i-th object
                jso := jsArr.Get(i) as TJsonObject;

                //enumerate object fields
                for jsPair in jso do begin
                    writeln('   ', jsPair.JsonString.Value, ': ', jsPair.JsonValue.Value);
                end;
            end;
        finally
            jsv.Free();
            readln;
        end;
    except
        on E: Exception do
          Writeln(E.ClassName, ': ', E.Message);
    end;
end.