4.6 -Component or Slider? "onValueChanged' is not a member of 'UnityEngine.Component"

In this snippet p is a RectTransform I have just instantiated.

It is a UI.panel, that contains 3 sliders.
When I do this:

var content = p.GetComponentsInChildren(UnityEngine.UI.Slider);
for (var sl : UnityEngine.UI.Slider in content)
{
print(sl.GetType()); // prints 'UnityEngine.UI.Slider'
sl.onValueChanged.AddListener(SetRadius);
}
print(content[0].GetType());// prints 'UnityEngine.UI.Slider'​

I get no error. The listener is added to the three sl sliders. And both sl and content[0] appear to be of the same type: UnityEngine.UI.Slider

If I try to do this however (in order to assign a different listener to each slider):

content[0].onValueChanged.AddListener(SetSpeed);​

I get an onValueChanged' is not a member of 'UnityEngine.Component error.

Why are content members identified as UnityEngine.UI.Slider when asked by GetType() yet considered a component when I address them with content[index]?

If I try to initialize my content variable like this:

var content : UnityEngine.UI.Slider[] = p.GetComponentsInChildren(UnityEngine.UI.Slider);

It passes first assembly, but at runtime, it throws the InvalidCastException: Cannot cast from source type to destination type. error.

This is very confusing. How do I access the members of content as UI.Sliders?

 

Ok Thanks Tim, but then why does this output UnityEngine.UI.Slider as its type?

print(content[0].GetType());​

((Slider)components) ?

Now, how do I cast to a different type (in Javascript)?
The following gives me an invalid cast exception at runtime:

var content : UnityEngine.UI.Slider[] = p.GetComponentsInChildren(UnityEngine.UI.Slider);​

This gives me a UnityEngine not a member of component error:

content[0].UnityEngine.UI.Slider.onValueChanged.AddListener(SetRadius);​

And this throws the Object reference is not set to an instance of an object error:

var content = p.GetComponentsInChildren(UnityEngine.UI.Slider) as UnityEngine.UI.Slider[];​

on the line where I do I do content[0].onValueChanged.AddListener(SetRadius);

 

Because the array is type Object[], but once you get the individual array items, they all know their own type. This is true of any inherited type.

 

OK, I found a way:
If I store my array element in a variable and cast that variable as a slider then it works....

var content = p.GetComponentsInChildren(UnityEngine.UI.Slider);
var sl1 : UnityEngine.UI.Slider = content[0];
sl1.onValueChanged.AddListener(SetRadius);

 

Your original code was working in the foreach because the loop was doing an implicit cast when it assigned a value to the 'sl' variable. It's basically the same as what you're doing now when you create a variable of type Slider and assign it a value from the content array.