On Wednesday, December 5, 2012 5:06:38 PM UTC+1, Sebastián Gurin wrote:
>
> Hi all.
>
> I'm playing with GWT overlay types for learning better ways of overlaying
> and working with them more agile. In particular I found that JSO setters
> methods that return 'this' for method chaining are a good way of defining
> an object state in a single Java statement, just like they are done in
> JavaScript. I written about this in
> http://cancerberonia.blogspot.com/2012/12/guidelines-for-writing-gwt-overlay-types.html
>
> This setters methods look like this:
>
> public native final MyJSO color(String val) /*-{
> this["color"]=val;
> return this;
> }-*/;
>
> So I can define an object in a single Java Statement like
>
> MyJSO my1 = MyJSO.create().color("red").age(14);
>
> I feel very confortable with that approach and using it on my GWT projects
> based on JSOs. But to my surprise (thanks to IRC user niloc132), these
> setters are not inlined in the GWT compiler JavaScript output. Please, read
> last part of my blog post "About Performance". For each setter a JavaScript
> function is defined and called: the JSNI code is not inlined. So this is
> not a zero overhead solution (as my libraries promise).
>
This last statement is misleading. JSOs do have zero-overhead, in the sense
that they do exactly what you tell them to do: the generated code looks the
same as the code you wrote, with no overhead due to having a Java class
translated to JS as is the case for non-JSO classes. The fact that some
methods are not inlined is not about overhead, it's about further
optimization.
In other words, your code is equivalent to this JS code, no overhead:
function color(o, val) {
o["color"] = val;
return o;
}
function age(o, val) {
o["age"] = val;
return o;
}
var my1 = age(color({}, "red") 14);
(actually, the "color" and "age" strings would be moved to global
variables, but that's another story)
> I tried different approachs for defining these setters, but with the same
> results in all cases. My question is, can I force the GWT compiler somehow
> to inline some of mine JSNI methods, perhaps with some annotation ? Do
> somebody have any suggestions for making setters returning 'this' to be
> inlined in javascript output instead of creating and calling javascript
> functions in javascript generated code ?
>
Either don't return "this":
MyJSO my1 = MyJSON.create();
my1.setColor("red");
my1.setAge(14);
or live with code that could be optimized further (and will probably be in
a future version of GWT; maybe it's already the case with the Closure
Compiler backend actually).
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