Exceptions

Rescue ... else ... ensure

• Handling exceptions
• Performing clean-up

begin
  statements
  rescue <class>
    statements
    [retry]
  else
    statements
  ensure
    statements
end

• The rescue clause is executed if a matching exception was raised
  
• The else clause is only executed if no exceptions are raised
• The ensure clause is always executed when the block terminates (even if an exception was raised)

• A retry statement within a rescue clause will repeat the entire block
  

Raise

• Raising exceptions
  

raise                              # Reraise the current exception
raise "text"                       # Raise a RuntimeError exception
raise CLASS, "text" [, caller]
raise OBJECT, "text" [, caller]

raise CLASS, "text", caller[m..n]

Catch ... throw

• throw causes the stack to be unwound until the catch block is reached

catch (:LABEL) do
  ...
  throw :LABEL
end