Architectural_Design_with_SketchUp

Chapter 6 Creating Geometry Using Ruby Scripting
Storing Stuff: Variables and Constants
As demonstrated, you can simply assign anything to a variable name of your choosing (e.g.,
a = 1.2). This works with a string, a float number, an integer, an array, or an object. You
don’t have to even declare the variable’s type as you often need to do in other programming
languages.
When using variables, start the name with a lowercase letter or an underscore (“_”).
Uppercase first letters are reserved for methods and constants (e.g., for PI). You can assign
constants, then, such as MYNAME = “Alex”.
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You can even mix types, for example, in your calculations:
a = 1.2
b = 2
a * b
# a float number
# an integer number
This correctly gives you 2.4 as the result. Just keep in mind that numbers stored as strings
don’t automatically convert in your calculations; use to_f (for float numbers) and to_i (for
integers) first. If you had started the three lines of code with a = “1.2” (with the quotation
marks, thereby defining this as a string), the calculation would not have worked. The last line
would then have to be changed to a.to_f * b instead.
A useful constant is __FILE__ (with two underscores on either side of the word FILE). It
always gives you the current Ruby file’s name and location.
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It is important to remember that these variables are local variables. This means that they
work only wherever they were declared (within a program or a function). If you need a variable
to work globally, add a dollar sign to the front: $a.
If you want to use a collection of items, it is often best to store them in an array. An array
can, for example, contain a set of coordinates, names, or values. There are two ways to add
elements to an array. Either do it when you create the array:
names = [“Michael”,”John”,”Agnes”]
or first create an empty array and then add elements (to the end):
names = []
names.push (“Michael”,”John”,”Agnes”)
If you want to access an element of an array, write (in our example) names[1] to get
“John”. Always remember that an array starts at index zero!
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