On 30 Jun 2010, at 18:26, Jeff Watkins wrote:
> Just out of curiosity, what's wrong with the idiomatic Javascript way of
> passing an object literal as your last constructor argument? So your example
> becomes:
>
> var stopButton = new ImageButton(this, {
> image: getImage('stop.png'),
> size: buttonSize,
> toolTip: 'Stop Running Scripts',
> onClick: stopAll
> });
>
> Granted, you wind up with an extra comma...
The difference of my proposal is that this would work with any constructor: All
the properties of the provided object literal would be mixed into the created
object. Your proposal would require special constructors for each type that
would accept an optional last argument containing an object with all these
properties. Each of these constructors would then have to iterate over the
properties and copy them over. I proposed to automate this, as from my
experience it appears to be something that would often be of great use.
Just to clarify. These two examples would produce the same result:
var stopButton = new ImageButton(this) {
image: getImage('stop.png'),
size: buttonSize,
toolTip: 'Stop Running Scripts',
onClick: stopAll
};
VS:
var stopButton = new ImageButton(this);
stopButton.image = getImage('stop.png');
stopButton.size = buttonSize;
stopButton.toolTip = 'Stop Running Scripts',
stopButton.onClick = stopAll;
The ImageButton constructor would not provide any magic itself, and it would
never actually see the object literal. This would work out of the box with any
constructor.
In this particular example, ImageButton is actually a Java class that is used
through Rhino's Java bridge feature. Setting image / size / toolTip properties
then internally calls the setImage / setSize / setToolTip bean property
setters. As far as I understand, the proposal by Allen Wirfs-Brock to use
Object.create for this would there not work for two reasons:
ImageButton.prototype is not available for such native java classes, and
overriding properties through new property definitions would not cause the
previous setters to be called.
Jürg
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