Tuesday, November 07, 2006

Metaprogramming with Ruby

Ruby is a dynamic language. You can create classes and methods at runtime. This is metaprogramming. You can write code that writes code.

Example: Data format driving the code, CSV file with header at the top.

file: people.txt
"Smith, John", 35, 175, "5'10"
"Ford, Anne", 49, 142, "5'4"
"Taylor, Burt", 55, 173, "5'10"
"Zubrin, Candace", 23, 133, "5'6"

1. The code must not change when a new attribute is added to the existing file or if we are given a different file with different attribute names.
2. The header values such as name and age must be treated as attribute names.

Create a class with a name derived from the file name. First line of the file must have list of attribute names. Checks that can added are: Check the attribute name is a legal Ruby method name, badly formed and missing data.

Given the file name we can create a class from its contents. So:

class_name = File.basename(file_name,".txt").capitalize # Create the class name
# e.g. "foo.txt" => "Foo"
klass = Object.const_set(class_name,Class.new)

No comments:

Post a Comment