Difference Between m and m.top in brightscript?

Question

This Difference available on Roku Forum. But I didn't Understand. Does anyone know this difference and its attribute?

Answer 1

I will try to explain it simple as I can:

Image that "m" is associative array. m.top would be default element of that associative array. Something like this:

m = {top : "value for top element"}

So now You would be able to call "m.top" and get the value for it.

Every xml component has it's own "m" added to it on creation.

In general - "m.top" in Brightscript is used to reference the xml component in which is used.

That's the reason You can do this: m.CustomComponent = m.top.findNode("CustomComponent")

This in turn will return a child component(with ID "Custom Component") of m.top.

This will also create a variable - m.CustomComponent that has component file scope.

You can also add an interface to the .xml component. In order to acces it, You would use: m.top.nameOfInterface.

To create a variable that has component scope with the interface value, You would use this:

m.interfaceValue = m.top.nameOfInterface

In short: m.CustomComponent or m.interfaceValue are variables with the component scope. And "m" is used to differentiate between various variable scopes.

m.top is reference to a component it self.

In general this concept is important for data scoping. Please check this file(especially on "Component scope" part) to understand more about it: https://developer.roku.com/en-gb/docs/developer-program/core-concepts/data-scoping.md

Answer 2

Let try to make it more simple. when you are using "m.something", means you are referencing the variable of component defined in ".brs" file. when you are using "m.top.something", means you are referencing the components or fields defined in ".xml" file. "m" is like "this" pointer in java.