Handling NULL JSON values in Delphi

test.pas

const
  CUSTOMERS = '{"customers":[{"name":"Olaf"},{"name":"Big Bird"}]}';
  CUSTOMERS_NULL = '{"customers":null}';

procedure TForm39.Button1Click(Sender: TObject);
var
  LContainer: TJSONValue;
  LCustomers: TJSONArray;
begin
  //Here, the value is not nil, so you can just go ahead with GetValue
  LContainer := TJSONObject.ParseJSONValue(CUSTOMERS);
  try
    LCustomers := LContainer.GetValue<TJSONArray>('customers');
    Assert(LCustomers.Count = 2);
  finally
    FreeAndNil(LContainer);
  end;

  // If the value can be null though, then specify a default - which can be "nil"
  LContainer := TJSONObject.ParseJSONValue(CUSTOMERS_NULL);
  try
    LCustomers := nil;
    LCustomers := LContainer.GetValue<TJSONArray>('customers', nil);
    Assert(LCustomers = nil);
  finally
    FreeAndNil(LContainer);
  end;

  // There is also TryGet, but that's probably slower and less convenient
  LContainer := TJSONObject.ParseJSONValue(CUSTOMERS_NULL);
  try
    LCustomers := nil;
    LContainer.TryGetValue('customers', LCustomers);
    Assert(LCustomers = nil);
  finally
    FreeAndNil(LContainer);
  end;