Google App Script dynamically defined custom functions

Question

How can I dynamically define custom function for spreadsheet from onOpen() function code?

• write a code...

function onOpen() {
  //var s = SoapService.wsdl("http://example.com/service.wsdl", "serv");
  //var funcs = s.getServerFunctions();
  var funcs = { "pow2": "function (v) { return v*v};" }
  for(var f in funcs)
  {
     this[f] = eval(funcs[f]) // define server functions as custom google-script functions for spreadsheet using this[function_name] = eval(function_code)
  }
}

• try to call =pow2() ("pow2" is a function name) from any cell
• get an error "#NAME" - undefined function

Answer 1

The GAS does not support dynamic functions calls from spreadsheets. As I wrote in my comment to the @Srik answer, a solution is to use a "static" dispatcher function which has 1st parameter the dynamic function name and starting from 2nd parameter are parameters of the dynamic function. In spreadsheet it will look like =callFunction("pow2", 3) or =callFunction("mul", 3, 1).

But there is another problem. It seems that the GAS internals instance the script every call of the script functions, which means, that dynamic function created in the onOpen function will be not visible in the other functions. The following code demonstrates it. A cell containing the =pow2static(3) contains the error: ReferenceError: "pow2" is not defined. (line XX) error text.

A workaround is to download dynamic functions source code in the onOpen function, store it in an intermediate storage - either Cache or ScriptDB or better a combination Cache + ScriptDB, search the code by the name in the intermediate storage and execute it inside of the "static" dispatch function.

function onOpen() {
  var funcs = { "pow2": "function (v) { return v*v};" }
  for(var f in funcs) {
    this[f] = eval(funcs[f]);
  }
}

function pow2static(val) {
  return pow2(val);
}