==============
With-statement
==============

Java7
=====

.. code-block:: java

  public class TryWithResource {
  
      public static void main(String[] args) {
          System.out.println("* sample of normal process");
          process(false);
          System.out.println("\n* sample of failed process");
          process(true);
      }
  
      static void process(boolean to_fail){
          try (
               AutoCloseable imp1 = new AutoCloseableImpl("first");
               AutoCloseable imp2 = new AutoCloseableImpl("second")) {
                  System.out.println("process");
                  if(to_fail){
                      System.out.println("failed");
                      throw new RuntimeException();
                  }
          } catch (Exception e) {
              System.out.println("catch:" + e);
          } finally {
              System.out.println("finally");
          }
      }
  }
  
  class AutoCloseableImpl implements AutoCloseable {
      String name;
      public AutoCloseableImpl(String name_) {
          this.name = name_;
          System.out.println("open: " + name);
      }
  
      @Override
      public void close() throws Exception {
          System.out.println("close: " + name);
      }
  }

::

  * sample of normal process
  open: first
  open: second
  process
  close: second
  close: first
  finally
  
  * sample of failed process
  open: first
  open: second
  process
  failed
  close: second
  close: first
  catch:java.lang.RuntimeException
  finally


C#
==

.. code-block:: csharp

  using System;
  
  
  
  class Program
  {
      static void Main()
      {
          try
          {
              Console.WriteLine("* sample of normal process");
              process(false);
              Console.WriteLine("\n* sample of failed process");
              process(true);
          }
          catch (ApplicationException e)
          {
              Console.WriteLine("caught: " + e.Message);
          }
          finally
          {
              Console.WriteLine("finally");
          }
      }
  
      static void process(bool to_fail)
      {
          using (
              MyClass c1 = new MyClass("first"),
                      c2 = new MyClass("second"))
          {
              Console.WriteLine("process");
  
              if (to_fail)
              {
                  Console.WriteLine("failed");
                  throw new ApplicationException();
              }
          }
          Console.WriteLine("finished");
      }
  }
  
  class MyClass : IDisposable
  {
      string name;
  
      public MyClass(String _name)
      {
          this.name = _name;
          Console.WriteLine("open: " + name);
      }
  
      void Dispose()
      {
          Console.WriteLine("close: " + name);
      }
  }

::

  * sample of normal process
  open: first
  open: second
  process
  close: second
  close: first
  finished
  
  * sample of failed process
  open: first
  open: second
  process
  failed
  close: second
  close: first
  caught: An application exception has occurred.
  finally


Python
======

.. code-block:: python

  class MyClass(object):
      def __init__(self, name):
          self.name = name
  
      def __enter__(self):
          print "open: " + self.name
  
      def __exit__(self, *args):
          if args[0]:
              print "close with error({}): {}".format(args[0], self.name)
          else:
              print "close: " + self.name
          return STOP_EXCEPTION
  
  
  def process(to_fail):
      with MyClass("first") as x, MyClass("second") as y:
          print "process"
          if to_fail:
              print "failed"
              raise RuntimeError
  
  
  STOP_EXCEPTION = True
  print "* sample of normal process"
  process(False)
  
  print "\n* sample of failed process() without re-raise"
  process(True)
  
  print "\n* sample of failed process() with re-raise"
  STOP_EXCEPTION = False
  process(True)

::

  * sample of normal process
  open: first
  open: second
  process
  close: second
  close: first
  
  * sample of failed process() without re-raise
  open: first
  open: second
  process
  failed
  close with error(<type 'exceptions.RuntimeError'>): second
  close: first
  
  * sample of failed process() with re-raise
  open: first
  open: second
  process
  failed
  close with error(<type 'exceptions.RuntimeError'>): second
  close with error(<type 'exceptions.RuntimeError'>): first
  Traceback (most recent call last):
    File "with_statement.py", line 64, in <module>
      process(True)
    File "with_statement.py", line 52, in process
      raise RuntimeError
  RuntimeError


Python
======

.. code-block:: python

  class Foo(object):
      def __init__(self, to_fail):
          print "init", to_fail
          self.to_fail = to_fail
          if to_fail:
              raise RuntimeError
  
      def __enter__(self):
          print "enter", self.to_fail
  
      def __exit__(self, *args):
          print "exit", self.to_fail, args[0]
  
  with Foo(False) as x, Foo(True) as y:
      print "Hello"

::

  init False
  enter False
  init True
  exit False <type 'exceptions.RuntimeError'>
  Traceback (most recent call last):
    File "with_statement2.py", line 27, in <module>
      with Foo(False) as x, Foo(True) as y:
    File "with_statement2.py", line 19, in __init__
      raise RuntimeError
  RuntimeError