Actually Jasper and Scott just pointed out some problems here. I mistyped (should have been return _x; from the getter). But also I didn't handle the case of binding, or setting via the property correctly here. So this modified pattern doesn't work. I may be remembering it wrong and Alex can correct me.
Richard On Jul 25, 2013, at 9:21 AM, Richard Bair <[email protected]> wrote: >> Regarding memory requirements of the "full lazy" properties, let me state >> the obvious: >> - if the property is not used at all, we have a reference and a double >> instead of just a reference (worse unless in bucket) >> - if getters/setters are called, we still have a reference and a double >> instead of full instantiated property (better) >> - if a listener is added, we have instantiated property and a double instead >> of just the property (slightly worse) >> So it looks like it would make best sense to introduce this for properties >> that are often get/set but usually don't have listeners on them. I'm not >> sure if such set exists and can be identified. > > Thanks Pavel, this is a good summary. Alex K. and I were looking at a pattern > for this once and he had another way to do it which was different than what I > had done in the past. The pattern I used to use was something like this: > > private double _x; > private DoubleProperty x; > > public final void setX(double value) { > if (x == null) { > _x = value; > } else { > x.set(value); > } > > public final double getX() { > return x == null ? _x : x.get(); > } > > public final DoubleProperty xProperty() { > if (x == null) x = new DoubleProperty(this, "x", _x); > return x; > } > > instead it could be done like this which results in faster getters (because > you never have to delegate to another method), an almost immeasurably slower > setter, and slightly little less code: > > private double _x; > private DoubleProperty x; > > public final void setX(double value) { > _x = value; > if (x != null) x.set(value); > } > > public final double getX() { > return x; > } > > public final DoubleProperty xProperty() { > if (x == null) x = new DoubleProperty(this, "x", _x); > return x; > } > > > The idea here is to always set the local field, so that we can always just > return the value immediately in the getter. Where I think this may make a > difference is on the smaller end systems (mobile / embedded) because from > previous analysis we saw that none of our getters were getting inlined -- we > actually paid the price of each method call overhead, because since we were > reading from the property objects and the property objects were a couple > methods worth of work for each getter call, the VM wouldn't inline the > generated code into the call sites. By using this pattern in places that are > commonly read, we would probably get these getters all inlined again and > avoid all the method call overhead entirely. > > Richard
