mORMot Open Source

Peter Evans

Member

Registered: 2016-07-03

Posts: 32

JSON record array on Android

Subject : JSON record array on Android

Hello All,

I have been able to manipulate JSON array of records on Windows.

However, on Android I can not generate the array of records from the JSON.

This pseudo code works on Windows :-

  TMyRecord = record
    CompanyId : String;
    ClientId  : String;
  end;

  TRecArray = record
    MyRecArray : array of TMyRecord;
  end;

  Rec1     : TMyRecord;
  Rec2     : TMyRecord;
  JsonStr  : String;
  RecArray : TRecArray;
begin
  Rec1.CompanyId := 'Company1';
  Rec1.ClientId  := 'Client1';

  Rec2.CompanyId := 'Company2';
  Rec2.ClientId  := 'Client2';

  JsonStr := '{"MyRecArray":[';
  JsonStr := JsonStr +
             SynCommons.RecordSaveJSON(
                          Rec1,
                          TypeInfo(TMyRecord));
  JsonStr := JsonStr + ',' +
             SynCommons.RecordSaveJSON(
                          Rec2,
                          TypeInfo(TMyRecord));
  JsonStr := JsonStr + ']}';

  SetLength(RecArray.MyRecArray, 2);
  bResult := SynCommons.RecordLoadJSON(
                            RecArray,
                            JsonStr,
                            TypeInfo(TRecArray));
end;

On Android I can get the JSON using :-

var
  RecVariant : Variant;
begin
  JsonStr := '{"MyRecArray":[';

  RecVariant := TMyRecord2Variant(Rec1);

  JsonStr := JsonStr +
             SynCrossPlatformJSON.ValueToJSON(RecVariant);

  RecVariant := TMyRecord2Variant(Rec2);

  JsonStr := JsonStr + ',' +
             SynCrossPlatformJSON.ValueToJSON(RecVariant);

  JsonStr := JsonStr + ']}';

  {The JsonStr is the same as on Windows}
end;

Now on Android generating the array of records (This does not work) :-

begin
  RecVariant := SynCrossPlatformJSON.JSONToValue(JsonStr);

  RecArray := Variant2MyRecordArray(RecVariant, 2); {Error in this call}
end;
 

function Variant2MyRecordArray(var   aRecVariant  : Variant;
                               const aRecsInArray : Integer) : TRecArray;
var
  iIterate : Integer;
  Str      : String;
begin
  if aRecsInArray <= 0 then begin
    SetLength(Result.MyRecArray, 0);
    Exit;
  end;
  SetLength(Result.MyRecArray, aRecsInArray);
  for iIterate := 0 to (aRecsInArray - 1) do begin
    Str := aRecVariant.MyRecArray[iIterate].CompanyId; {Error - Variant method calls not supported}

    Result.MyRecArray[iIterate].CompanyId := Str;
    ...
  end;
end;       

This last part in Android doesn't work.
Perhaps there is a simpler way to achieve this on Android?

Any ideas?

Regards,
  Peter G. Evans

Peter Evans

Member

Registered: 2016-07-03

Posts: 32

Re: JSON record array on Android

The JSON is this :-

{"MyRecArray":[{"CompanyId":"Company1","ClientId":"Client1"},{"CompanyId":"Company2","ClientId":"Client1"}]}

This JSON validates at the website JSONLint.

Peter Evans

Member

Registered: 2016-07-03

Posts: 32

Re: JSON record array on Android

I now have a solution for Android. This is :-

var
  RecsInArray    : Integer;
  iLen           : Integer;
  KindJSON       : SynCrossPlatformJSON.TJSONVariantKind;
  RecVariantData : SynCrossPlatformJSON.TJSONVariantData;
begin
  RecsInArray := 2;
  {Need to pass an array.
  So remove leading characters. Do not worry about trailing bracket}
  iLen := Length('{"MyRecArray":');
  { your routine here to remove leading characters from JSONStr }

  RecVariantData.Init(JSONStr);
  KindJSON := RecVariantData.Kind;
  if KindJSON <> jvArray then
    Exit;
  if RecVariantData.Count <> RecsInArray then
    Exit;

  SetLength(RecArray.MyRecArray, RecsInArray);

  RecArray.MyRecArray[0] := Variant2MyRecord(RecVariantData.Item[0]);
  RecOut1 := RecArray.MyRecArray[0]; {test}

  RecArray.MyRecArray[1] := Variant2MyRecord(RecVariantData.Item[1]);
  RecOut2 := RecArray.MyRecArray[1]; {test}
end;

james6

Member

Registered: 2017-09-12

Posts: 1

Re: JSON record array on Android

Validate it here: json parser