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The String class has many methods, which I ll cover in the next chapter, but experiment with some of the following: capitalize, downcase, chop, hash, next, reverse, sum, or swapcase. Table 2-1 demonstrates some of the methods available to strings. Table 2-1. The Results of Using Different Methods on the String "Test" Expression

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The self parameter (mentioned in the previous section) is, in fact, what distinguishes methods from functions. Methods (or, more technically, bound methods) have their first parameter bound to the instance they belong to: you don t have to supply it. So while you can certainly bind an attribute to a plain function, it won t have that special self parameter: >>> class Class: def method(self): print 'I have a self!' >>> def function(): print "I don't..." >>> instance = Class() >>> instance.method() I have a self! >>> instance.method = function >>> instance.method() I don't... Note that the self parameter is not dependent on calling the method the way I ve done until now, as instance.method. You re free to use another variable that refers to the same method: >>> class Bird: song = 'Squaawk!' def sing(self): print self.song >>> bird = Bird() >>> bird.sing() Squaawk! >>> birdsong = bird.sing >>> birdsong() Squaawk! Even though the last method call looks exactly like a function call, the variable birdsong refers to the bound method bird.sing, which means that it still has access to the self parameter.

"Test" + "Test" "Test".capitalize "Test".downcase "Test".chop "Test".hash "Test".next "Test".reverse "Test".sum "Test".swapcase "Test".upcase "Test".upcase.reverse "Test".upcase.reverse.next

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Some of the examples in Table 2-1 are obvious, such as changing the case of the text or reversing it, but the last two examples are of particular interest. Rather than processing one method against the text, you process two or three in succession. The reason you can do this is that methods will return the original object after it s been adjusted by the method, so you have a fresh String object upon which to process another method. "Test".upcase results in the string TEST being returned, upon which the reverse method is called, resulting in TSET, upon which the next method is called, which increments the last character, resulting in TSEU. In the next chapter we ll be looking at strings more deeply, but the concept of chaining methods together to get quick results is an important one in Ruby. You can read the preceding examples aloud and they make sense. Not many other programming languages can give you that level of instant familiarity!

So far in this chapter we ve looked at several reasonably complex concepts. With some programming languages, object orientation is almost an afterthought, and beginners books for these languages don t cover object orientation until readers understand the basics of the language (particularly with Perl and PHP, popular Web development languages). However, this doesn t work for Ruby because Ruby is a pure object-oriented language, and you can gain significant advantages over users of other languages by understanding these concepts right away. Ruby has its roots in other languages though. Ruby has been heavily influenced by languages such as Perl and C, both usually considered procedural non object-oriented languages (although Perl has some object-oriented features). As such, even though almost everything in Ruby is an object, you can use Ruby in the same way as a non object-oriented language if you like, even if it s less than ideal. A common demonstration program for a language such as Perl or C involves creating a subroutine (essentially a sort of method that has no associated object or class) and calling it, much like you called the bark method on your Dog objects. Here s a similar program, written in Ruby: