evaluate static method

Implementation

static dynamic evaluate(String? expression, {Map<String?, dynamic>? variables, Map<String?, dynamic>? altFunctions})
{
  if (expression == null) return null;

  var result;
  var _expression = expression;
  var _parsed;
  var i = 0;
  var _variables = Map<String, dynamic>();
  var _functions = Map<String?, dynamic>();

  try
  {
    // setup variable substitutions
    if (variables != null)
    variables.forEach((key,value)
    {
      i++;
      var _key = "___V$i";
      _variables[_key] = _isNumeric(value) ? _toNum(value) : _isBool(value) ? _toBool(value) : value;
      _expression = _expression.replaceAll(key!, _key);
    });

    // add variables
    _functions.addAll(_variables);

    // add functions
    _functions.addAll(functions);

    // add alternate functions that dont clash
    altFunctions?.forEach((key, value) => _functions.containsKey(key) ? null : _functions[key] = value);

    // parse the expression
    _parsed  = Expression.tryParse(_expression);

    // failed parse?
    if (_parsed == null) throw(Exception('Failed to parse $_expression'));

    // required to replace quoted string observables
    _parsed = replaceInLiterals(_parsed, _variables);

    // evaluate the expression
    result = evaluator.eval(_parsed, _functions);
  }
  catch(e)
  {
    String? msg;
    if (variables != null) variables.forEach((key, value) => msg = (msg ?? "") + (msg == null ? "" : ",  ") + "$key=${value.toString()}");
    Log().debug("eval($expression) [$msg] failed. Error is $e");
    result = null;
  }
  return result;
}