What Is the &: of &:Afunction Doing

What is the &: of &:aFunction doing?

is there any way of passing variables into trigger

No.

You're invoking Symbol#to_proc which does not allow you to specify any arguments. This is a convenient bit of sugar Ruby provides specifically for invoking a method with no arguments.

If you want arguments, you'll have to use the full block syntax:

anArray.each do |i|
  i.trigger(arguments...)
end

How do I call a function inside of another function?

function function_one() {

    function_two(); // considering the next alert, I figured you wanted to call function_two first

    alert("The function called 'function_one' has been called.");

}

function function_two() {

    alert("The function called 'function_two' has been called.");

}

function_one();

What's the difference between a method and a function?

A function is a piece of code that is called by name. It can be passed data to operate on (i.e. the parameters) and can optionally return data (the return value). All data that is passed to a function is explicitly passed.

A method is a piece of code that is called by a name that is associated with an object. In most respects it is identical to a function except for two key differences:

1. A method is implicitly passed the object on which it was called.
2. A method is able to operate on data that is contained within the class (remembering that an object is an instance of a class - the class is the definition, the object is an instance of that data).

(this is a simplified explanation, ignoring issues of scope etc.)

What is the meaning of returning a function from another function?

Currently, the object which you are returning is the function.
In this context, variable add contains a reference to the function which you have to invoke.

What is the best way to exit a function (which has no return value) in python before the function ends (e.g. a check fails)?

You could simply use

return

which does exactly the same as

return None

Your function will also return None if execution reaches the end of the function body without hitting a return statement. Returning nothing is the same as returning None in Python.

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