Hi all,
This is a pretty common in the JS world, but take a look at this JS library
<https://github.com/bevacqua/dragula>, which as part of its API has
settings/options for configuration, where options are done with something
with JS structure like:
*{*
* ...*
* isContainer: function (el) { return false; }, *
* moves: function (el, source, handle, sibling) { return true; }, *
*}*
As you can see the callbacks have defaults that allows JS developers not to
bother specifying them. Pretty neat! This is accomplished with code like:
function always () { return true; }
var o = options || {};
if (o.moves === void 0) { o.moves = always; }
Now, when I wrap such options object it in JsInterop:
*@JsType(isNative = true, name = "Object", namespace = JsPackage.GLOBAL)*
*class Options {*
...
* @JsProperty*
* public CallbackRet1<Boolean, Object> isContainer;*
* @JsProperty*
* public CallbackRet4<Boolean, Object, Object, Object, Object> moves;*
* /** We need this trivial defaults to be singletons */*
* public static final CallbackRet1<Boolean, Object> DEFAULT_IS_CONTAINER
= o->false;*
* public static final CallbackRet4<Boolean, Object, Object, Object,
Object> DEFAULT_MOVES = (o1,o2,o3,o4)->true;*
* /** A factory methods to set the defaults. Uh-oh!*/*
* @JsOverlay*
* final static public Options createDefault() {*
* Options o = new Options();*
* o.isContainer = DEFAULT_IS_CONTAINER;*
* o.moves = DEFAULT_MOVES;*
* return o; *
* }*
*}*
Do I have to provide defaults for callbacks and other properties? As you
can see my current approach leads to verbose code and the *getDeafult()*
method that I would really like to avoid.
What happens if I leave the properties uninitialized? What will the JS API
see with such partially supplied options - undefined or null? I tried
putting @JsOptional on all of these properties, but this annotations in not
meant for members.
What is the best strategy to handle such cases with JsInterop?
Also, why is JsInterop not allowing me to initialize the fields at
declaration?
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