Ruby journey (16) exception handling rescue and ensure

Begin # Start
 
  Raise .. # Throw an exception
 
Rescue [exceptiontype = standardexception] # Capture exceptions of the specified type. The default value is standardexception.
$! # Exception Information
$ @ # Indicates that an exception occurs.CodeLocation
Else   # Other exceptions
..
Ensure # Enter the code block whether there are any exceptions.
 
End # End

This is an exception handling structure, which can be combined with $! Cause of the error, and make a small error capture and prompt at $ @ error locationProgramFor example

Begin
Puts
Puts " File: # {name = argv. Shift} "
File = Open (name)
I = 0
File. Read. each_line { | Line | Puts " # {I + = 1}. # {Line} " }
Puts
Rescue
Puts " Error: # {$ !} At :#{$ @} "
Ensure
File. Close
End

The preceding applet reads a specified file and adds the row number to output the file. When an error is generated, an error message and a prompt are displayed. You can intentionally enter a non-existent file name.

Actually, begin is equivalent to a try of C #.
Rescue is equivalent to catch of C #
Ensure is equivalent to finaly of C #.
Raise is equivalent to the throw of C #.

Structure of exception classes

 

Exception

Object

• Exception
  • (Interrupt) (Ruby 1.7 featuresLocation before version 1.6)
  • Nomemoryerror
  • Scripterror
    • Loaderror
    • (Nameerror) (Ruby 1.7 featuresLocation before version 1.6)
    • Notimplementederror
    • Syntaxerror
  • Signalexception
    • Interrupt (Ruby 1.7 features)
  • Standarderror
    • Argumenterror
    • Indexerror
      • Keyerror (Ruby 1.9 features)
    • Ioerror
      • Eoferror
    • Localjumperror
    • Nameerror (Ruby 1.7 features)
      • Nomethoderror (Ruby 1.7 features)
    • Rangeerror
      • Floatdomainerror
    • Regexperror
    • Runtimeerror
    • Securityerror
    • Systemcallerror
      • Errno: exxx
    • Systemstackerror
    • Threaderror
    • Typeerror
    • Zerodivisionerror
  • Systemexit
  • Fatal