Ruby in a Nutshell

Built-in Functions

Since the Kernel module is included by Object class, its methods are available everywhere in the Ruby program. They can be called without a receiver (functional form), therefore, they are often called functions.

abort

Terminates program. If an exception is raised (i.e., $! isn’t nil), its error message is displayed.

Array(obj)

Returns obj after converting it to an array using to_ary or to_a.

at_exit {...}

Registers a block for execution when the program exits. Similar to END statement (referenced in Section 2.8), but END statement registers the block only once.

autoload(classname, file)

Registers a class classname to be loaded from file the first time it’s used. classname may be a string or a symbol.

autoload :Foo, "foolib.rb".

binding

Returns the current variable and method bindings. The Binding object that is returned may be passed to the eval method as its second argument.

block_given?

Returns true if the method was called with a block.

callcc {|c|...}

Passes a Continuation object c to the block and executes the block. callcc can be used for global exit or loop construct.

def foo(c)
  puts "in foo"           #
  c.call                  # jump out
  puts "out foo"          # this line never be executed
end
callcc{|c| foo(c)}        # prints "in foo"

caller([n])

Returns the current execution stack in an array of the strings in the form file:line. If n is specified, returns stack entries from nth level on down.

catch(tag) {...}

Catches a nonlocal exit by a throw called during the execution of its block.

def throwing(n) ...