Declaring class differently for different Dojo versions without duplicating code?

Question

I have an iWidget designed for IBM Connections, and my javascript code depends on Dojo (which is included by default in Connections).
It currently works in Connections 4.0 and 4.5, but is broken in Connections 5.0 (released last week), as Dojo has been updated to v1.9 and complains about my use of dojo.require.

These messages appear in the browser console when my widget tries to load on Connections 5.0:

Avoid calling dojo.require() to load classes at runtime, use net.jazz.ajax.xdloader.load_async() instead. Function '(anonymous)' required class 'dojox.atom.io.model'.
Avoid calling dojo.require() to load classes at runtime, use net.jazz.ajax.xdloader.load_async() instead. Function '(anonymous)' required class 'dojox.atom.io.Connection'.

I want to make conditional code that uses different ways of defining my widget class and requiring other Dojo modules depending on the Dojo version.

The widget javascript currently looks like this:

dojo.provide('insightCommunityWidgetClass');
dojo.require('dojox.atom.io.model');
dojo.require('dojox.atom.io.Connection');

dojo.declare('insightCommunityWidgetClass',null,{
    // Class fields and methods. Currently 680 lines uncompressed.
});

I haven't yet created a version that works with Dojo 1.9 / Connections 5.0, but I think it would look something like this (and I'll have to make my javascript file name match the desired class name):

define(['dojo/_base/declare','dojox.atom.io.model','dojox.atom.io.Connection'], function(declare){
    return declare(null, {
        // Class fields and methods.
    });
});

How can I have both of these in one file and choose between them without duplicating the class body?

Update:
I've attempted some conditional code, checking (define && define.amd) as suggested by Dimitri, tested this on Connections 4.0 and 4.5, and am getting very weird behaviour.

Temporarily ignoring any attempt to not duplicate my class, here's some conditional code which I've used exactly as shown, with a severely reduced widget class:

if (define && define.amd) {
    console.log('Declaring insightWidgetClass with AMD (new method).');
    define(['dojo/_base/declare','dojox/atom/io/model','dojox/atom/io/Connection'],
        function(declare){
            return declare(null,{
                SVC_INV: 1,
                onLoad: function() {
                    console.log('insightWidgetClass onLoad.');
                }
            });
        }
    );

} else {
    console.log('Declaring insightWidgetClass with dojo.declare (old method).');
    dojo.provide('insightWidgetClass');
    dojo.require('dojox.atom.io.model');
    dojo.require('dojox.atom.io.Connection');

    dojo.declare('insightWidgetClass',null,{
        SVC_INV: 1,
        onLoad: function() {
            console.log('insightWidgetClass onLoad.');
        }
    });
}

This seems not to run at all. None of my console.log messages appear in the browser console.

If I comment out the conditionals and make it so the only active code is the block after else, it runs. I get the "declaring ... (old method)" and the "insightWidgetClass onLoad" console messages.

I thought maybe enclosing the Dojo provide, require and declare calls in any kind of block might cause a problem, so I tested just putting the working code in an if (true) { block, and it still works.

The last things I've tried at this point are adding this one line before everything else, to see what define is:

console.log('dojo define',define);

... which breaks it. No console messages at all from my code.
Then I remove the define argument from that new line, so it's only sending a string to the console, and the code works again.
It seems like any mention of a define identifier silently stops the rest of the code from running.
There are no errors or warnings in the console indicating a problem. All I can say to that is: WTF?!

Now back to checking dojo.version instead.

Answer 1

Normally both should still work, dojo.provide() and dojo.require() are deprecated, but not entirely removed. Just make sure that your loading dojo in synchronous mode.

Besides that, the AMD way of coding is introduced in Dojo 1.7, which means that it should be supported on IBM Connections 4.5 as well (though I don't know about IBM Connections 4).

But if you really want to use both code bases, you can simply refer to the same object in stead of duplicating it, for example:

var myModule = {
    // Class fields and methods.
};
if (dojo.version.major == 1 && dojo.version.minor == 9) {
    define(['dojo/_base/declare','dojox.atom.io.model','dojox.atom.io.Connection'], function(declare){
        return declare(null, myModule);
    });
} else {
    dojo.provide('insightCommunityWidgetClass');
    dojo.require('dojox.atom.io.model');
    dojo.require('dojox.atom.io.Connection');

    dojo.declare('insightCommunityWidgetClass',null, myModule);  
}

Or you could use the following check:

if (typeof define === 'function' && define.amd) {
    // AMD style code
} else {
    // Non-AMD style code
}

This is the approach most cross-loader libraries use. Libraries that work both on AMD loaders (Dojo, Require.js), but also on Node.js or simply by using global namespacing use a similar piece of code to determine how they load their module.