This chapter addresses a few practical issues.

Statement delimiters

Some languages require some kind of punctuation, often a semicolon (

;

sh

Our Fruit class from the previous chapter had two instance variables, one to describe the kind of fruit and another to describe its condition. It was only after writing a custom

inspect

What is an accessor?

We briefly discussed instance variables in an earlier chapter, but haven't done much with them yet. An object's instance variables are its attributes, the things that distinguish it from other objects of the same class. It …

There may be cleanup work that is necessary when a method finishes its work. Perhaps an open file should be closed, buffered data should be flushed, etc. If there were always only one exit point for each method, we could …

An executing program can run into unexpected problems. A file that it wants to read might not exist; the disk might be full when it wants to save some data; the user may provide it with some unsuitable kind of …

A constant has a name starting with an uppercase character. It should be assigned a value at most once. In the current implementation of ruby, reassignment of a constant generates a warning but not an error (the non-ANSI version of …

A local variable has a name starting with a lower case letter or an underscore character (_). Local variables do not, like globals and instance variables, have the value nil before initialization:

ruby> $foo
   nil
ruby> @foo
   nil
ruby> foo …

An instance variable has a name beginning with @, and its scope is confined to whatever object self refers to. Two different objects, even if they belong to the same class, are allowed to have different values for their instance …

A global variable has a name beginning with $. It can be referred to from anywhere in a program. Before initialization, a global variable has the special value nil.

ruby> $foo
   nil
ruby> $foo = 5
   5
ruby> $foo
   5 …

Ruby has three kinds of variables, one kind of constant and exactly two pseudo-variables. The variables and the constants have no type. While untyped variables have some drawbacks, they have many more advantages and fit well with ruby's quick and …