[TIMOB-25806] iOS: Fix arrow-functions in Hyperloop

[hansemannn]

JIRA: https://jira.appcelerator.org/browse/TIMOB-25806

We may add more tests for other ES6 styles, like rest parameters.

[sgtcoolguy]

So this is correct, but we probably also need to support 'FunctionDeclaration'.

According to estree, the possible AST node types for a function include that as well: https://hexdocs.pm/estree/ESTree.Function.html#content

[hansemannn]

I couldn't find the FunctionDeclaration type in the AST-parser we use (and the logs I tried). Maybe move this to your ES6 PR?

[sgtcoolguy]

A function declaration is simply a function defined standalone, versus being part of some other statement/assignment:

declaration:

function myFunc() {
  // whatever
}

expression:

var myFunc = function () {
  // whatever
};

more: https://javascriptweblog.wordpress.com/2010/07/06/function-declarations-vs-function-expressions/

[hansemannn]

There is still no FunctionDeclaration type in the AST-parser library from what I see, so should we handle it manually?

[sgtcoolguy]

We use acorn, right? https://github.com/acornjs/acorn/blob/4d1230699be387e31250735cf43f0723ac747007/src/statement.js#L520

[sgtcoolguy]

Ah, now I see why you'd never run into it - the way this is called, I think is typically on the right-hand side of a variable declaration. I suppose if we run into the case we can add it.

[hansemannn]

Ok cool! There is still some weird issue with the scope, where this.buttonPressed would not be found:

    var ButtonDelegate = Hyperloop.defineClass('ButtonDelegate', 'NSObject');

    ButtonDelegate.addMethod({
        selector: 'buttonPressed:',
        instance: true,
        arguments: ['UIButton'],
        callback: (sender) => {
            // Not existing with ES6 enabled
            if (this.buttonPressed) {
                this.buttonPressed(sender);
            }
        }
    });

    var delegate = new ButtonDelegate();
   
    // Not called with ES6 enabled
    delegate.buttonPressed = function(sender) {
        alert('Button pressed!');
    };

Its a different kind of issue, so maybe we need to restructure the example to not use this kind of "method-assignments".

Funny enough: If the delegate is in a different file like here, it works. It's tracked in TIMOB-25807.