ASP.NET Web PDF Document Viewer/Editor Control Library

The end line should be of obvious utility. It matches up with the class definition on the first line and tells Ruby that you re no longer defining the Person class. To recap, a class defines a concept (such as a Person), and an object is a single thing based on a class (such as a Chris or a Mrs. Smith ). So let s experiment with our Person class. Go to your irb prompt and type in the Person class found earlier. Your efforts should look like this:

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Now you ve cleared the basics. You can implement any algorithm you can dream up; you can read in parameters and print out the results. In the next couple of chapters, you learn about something that will help you write larger programs without losing the big picture. That something is called abstraction.

irb(main):001:0> class Person irb(main):002:1> attr_accessor :name, :age, :gender irb(main):003:1> end => nil irb(main):004:0>

A search for the term runners on iStockphoto resulted in a number of good aesthetic matches with this audience, so add one to the Setting slide, as shown on the upper left in Figure 9-8, and then send the headline behind the photograph, as you ll do on the rest of the Act I slides. Then search for stopwatch, and add the photo to the Role slide (upper right). A search for hurdles did not result in photos with three hurdles as the sketch described, but a single hurdle will work ne on the Point A slide (lower left). A search for nish line did not turn up a match for the sketch either, but a picture of a running track will work, along with a banner shape added using the PowerPoint 2007 drawing tools and showing the words Finish Line, as shown on the Point B slide (lower right). As these examples demonstrate, you won t always nd the perfect match for your sketches, but you ll likely nd something that will work.

You ll notice that the digit at the end of each irb prompt line changed when you were entering the class code. The reason for this is that when you pressed Enter for the class Person line, Ruby knew that you were now within a class structure, defining a class, rather than typing code to be processed immediately. The 1 represents that you re at a depth of 1 of nested concepts. If this doesn t make sense to you now, don t worry, as I ll be covering this in more detail later. Once you ve finished your class definition and Ruby has processed it, nil is returned, because defining a class results in no return value, and nil is Ruby s way of representing nothing. As there were no errors, your Person class now exists within Ruby, so let s do something with it:

Ruby s standard library includes a module called Benchmark. Benchmark provides several methods that measure the speed it takes to complete the code you provide. For example:

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require 'benchmark' puts Benchmark.measure { 10000.times { print "." } }

n this chapter, you learn how to group statements into functions, which enables you to tell the computer how to do something, and to tell it only once. You won t have to give it the same detailed instructions over and over. The chapter provides a thorough introduction to parameters and scoping; you learn what recursion is and what it can do for your programs, and you see how functions themselves can be used as parameters, just like numbers, strings, and other objects.

This code measures how long it takes to print 10,000 periods to the screen. Ignoring the periods produced, the output (on my machine; yours might vary) is as follows: