2 Objects, methods, and local variables

Ruby programming is centered on objects, and this chapter introduces the idea that writing Ruby means creating objects, sending them messages, and defining methods that carry out those messages. A generic object can be created with Object.new, then extended with custom behavior by defining methods directly on it. The chapter emphasizes that objects are the main units of design and action in Ruby, while classes are introduced as a supporting concept that will be explored later.

The chapter then explains how method calls work, including arguments, return values, and Boolean-style methods. It distinguishes between parameters in a method definition and arguments passed at call time, shows how methods can accept required, optional, and variable numbers of arguments, and explains how Ruby assigns them. It also demonstrates that every method call returns a value, usually the last evaluated expression, and that Ruby provides tools like string interpolation, question-mark method names, and conditional logic to make object behavior expressive and readable.

Finally, the chapter turns to local variables and object references, showing that variables do not hold objects themselves but references to objects. This helps explain why changing an object through one variable affects all variables that point to it, while reassignment simply makes a variable refer to a new object. The chapter also explores how Ruby interprets bare identifiers as keywords, local variables, or method calls, and introduces useful introspective and defensive methods such as object_id, respond_to?, send, dup, clone, and freeze for understanding and controlling object behavior.