koobas.hobune.stream
Unityscript - Using "as" to cast for GetComponentsInChildren returns empty array
I have an instantiated GameObject with multiple ParticleSystems on it (each on a GameObject that is a child of the main GameObject). To stop the entire thing from emitting further particles, I use this:
function StopEmission(theParticleObject : GameObject) {
var tempComponents : Component[];
tempComponents = theParticleObject.GetComponentsInChildren(ParticleSystem);
for (var particle : ParticleSystem in tempComponents) {
particle.enableEmission = false;
}
}
However this generates an "implicit downcast" warning. I understand I should be able to cast out the error as follows:
var tempComponents : ParticleSystem[] = theParticleObject.GetComponentsInChildren(ParticleSystem) as ParticleSystem[];
for (var particle : ParticleSystem in tempComponents) {
particle.enableEmission = false;
}
However, the for loop in this case never returns any results and I'm not sure why. I believe "`as`" will return null when the casting fails, but why shouldn't this work?
EDIT: This doesn't work either, harrumph:
var tempComponents : Component[];
tempComponents = theParticleObject.GetComponentsInChildren(ParticleSystem);
for (var particle : ParticleSystem in tempComponents as ParticleSystem) {
particle.enableEmission = false;
}
Not sure if this will help as I've never done anything like this.
The first example looks fine except for
var tempComponents : Component[];
You should start by using the first example, but change that line to
var tempComponents : ParticleSystem[];
When using GetComponent in uJS you can declare the parameter as a string or as a component type
theParticleObject.GetComponentsInChildren( ParticleSystem );
theParticleObject.GetComponentsInChildren( "ParticleSystem" ) as ParticleSystem;
you only need to append the as when you are using the string format.
For your second example, I think it is falling down because of the typecasting you use
var tempComponents : ParticleSystem[] = theParticleObject.GetComponentsInChildren(ParticleSystem) as ParticleSystem[];
should be
var tempComponents : ParticleSystem[] = theParticleObject.GetComponentsInChildren(ParticleSystem) as ParticleSystem;
though I could be very wrong about that!
You are populating an array of ParticleSystems, but each component is just a ParticleSystem.
Again the same rule applies : if you are not declaring the parameter as a string then you don't need to use as :
var tempComponents : ParticleSystem[] = theParticleObject.GetComponentsInChildren( ParticleSystem );
Finally you can remove any downcast warnings by using
#pragma downcast
but personally I never do this myself, it just masks the issues you have, I really don't know if pragma downcast fixes the problems on building, but in C# you definitely don't get away with incorrect typecasting =]
Downcasting isn't a problem, it's just a warning that you might not have intended it.
Aah, thankyou, that is great information. I was holding my breath after your answer, wondering if and what I got wrong.
Oh, and you would want to type as ParticleSystem[] rather than ParticleSystem (or rather, you would if that worked); it's an array, so trying to cast an array as a not-array would result in an error.
Also, the casting doesn't really have anything to do with strings; GetComponentsInChildren() always returns Component[] regardless. So the casting doesn't work for whatever reason. That's why it's better to use GetComponentsInChildren.(), since that does cast as an array of the correct type.
Use the generic version of GetComponentsInChildren; that way the array is automatically cast to ParticleSystem:
function StopEmission (theParticleObject : GameObject) {
var tempComponents = theParticleObject.GetComponentsInChildren.<ParticleSystem>();
for (var particle in tempComponents) {
particle.enableEmission = false;
}
}
Bingo! That did it; thanks Eric. Why does GetComponentsInChildren(ParticleSystem) exist if only GetComponentsInChildren.ParticleSystem>(); works "properly?"
GetComponentsInChildren.() was added later. The non-generic version does work properly, just not conveniently. ;) (I rarely ever want to deal with Component.)
