Video and slides synchronized, mp3 and slide download available at URL http://bit.ly/14ExI0I. Greg Young discusses eight lines of very common code finding in them massive numbers of dependencies and difficulties, looking for ways to get rid of them. Filmed at qconlondon.com. Greg Young is an independent consultant and entrepreneur. He is always involved with many concurrent projects, currently these include building out a distributed event store and mighty moose (a continuous test runner). For periods of years Greg has been known to stop living anywhere and just travel. Twitter: @gregyoung

1. 8
Lines
of
Code
Greg
Young

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http://www.infoq.com/presentations
/8-lines-code-refactoring

3. Presented at QCon London
www.qconlondon.com
Purpose of QCon
- to empower software development by facilitating the spread of
knowledge and innovation
Strategy
- practitioner-driven conference designed for YOU: influencers of
change and innovation in your teams
- speakers and topics driving the evolution and innovation
- connecting and catalyzing the influencers and innovators
Highlights
- attended by more than 12,000 delegates since 2007
- held in 9 cities worldwide

4. Simplicity

5. I
am
stupid
to
work
otherwise.
Fancy
code
befuddles
me.

6. public
class
DeactivateInventoryItem
{
private
readonly
ItemRepository
repository;
public
DeactivateInventoryItem(ItemRepository
repository)
{
this.repository
=
repository;
}
public
void
Deactivate(Guid
id,
string
reason)
{
var
item
=
repository.GetById(id);
item.Deactivate(reason);
repository.Save(item);
}
}

7. [Transactional]
[RequiresPermission(“admin”)]
[Logged]
[EatsExceptions]
[DoesBadThingsWhenYouArentWatching]
public
class
DeactivateInventoryItem
{
private
readonly
ItemRepository
repository;
public
DeactivateInventoryItem(ItemRepository
repository)
{
this.repository
=
repository;
}
public
void
Deactivate(Guid
id,
string
reason)
{
var
item
=
repository.GetById(id);
item.Deactivate(reason);
}
}

8. Simplicity?

9. <bean
id="moreComplexObject"
class="example.ComplexObject">
<!-­‐-­‐
results
in
a
setAdminEmails(java.uNl.ProperNes)
call
-­‐-­‐>
<property
name="adminEmails">
<props>
<prop
key="administrator">administrator@example.org</prop>
<prop
key="support">support@example.org</prop>
<prop
key="development">development@example.org</prop>
</props>
</property>
<!-­‐-­‐
results
in
a
setSomeList(java.uNl.List)
call
-­‐-­‐>
<property
name="someList">
<list>
<value>a
list
element
followed
by
a
reference</value>
<ref
bean="myDataSource"
/>
</list>
</property>
<!-­‐-­‐
results
in
a
setSomeMap(java.uNl.Map)
call
-­‐-­‐>
<property
name="someMap">
<map>
<entry
key="an
entry"
value="just
some
string"/>
<entry
key
="a
ref"
value-­‐ref="myDataSource"/>
</map>

10. [Transactional]
[RequiresPermission(“admin”)]
[Logged]
[EatsExceptions]
[DoesBadThingsWhenYouArentWatching]
public
class
DeactivateInventoryItem
{
private
readonly
ItemRepository
repository;
public
DeactivateInventoryItem(ItemRepository
repository)
{
this.repository
=
repository;
}
public
void
Deactivate(Guid
id,
string
reason)
{
var
item
=
repository.GetById(id);
item.Deactivate(reason);
}
}

11. [Transactional]
[RequiresPermission(“admin”)]
[Logged]
[EatsExceptions]
[DoesBadThingsWhenYouArentWatching]
public
class
DeactivateInventoryItem
{
private
readonly
ItemRepository
repository;
public
DeactivateInventoryItem(ItemRepository
repository)
{
this.repository
=
repository;
}
public
virtual
void
Deactivate(Guid
id,
string
reason)
{
var
item
=
repository.GetById(id);
item.Deactivate(reason);
}
}

12. public
object
Foo()
{
return
this;
}

14. If
you
find
you
need
an
extension
to
your
ide
to
understand
what’s
going
on.
Its
probably
not
simple.

15. What’s
the
root
of
the
problem?

16.
public
void
Deactivate(Guid
id,
string
reason)
{
var
item
=
repository.GetById(id);
item.Deactivate();
}
public
void
Reactivate(Guid
id,
DateTime
effective,
string
reason)
{
var
item
=
repository.GetById(id);
item.Deactivate();
}
public
void
CheckIn(Guid
id,
int
count)
{
var
item
=
repository.GetById(id);
item.Deactivate();
}

17. No
common
interface!

18.
public
void
Log(PointCut
calledOn)
{
logger.Log(calledOn.Name
+
“:”
+
calledOn.Parameters);
}

19.
public
void
Handle(DeactivateCommand
c)
{
var
item
=
repository.GetById(c.id);
item.Deactivate();
}
public
void
Handle(ReactivateCommand
c)
{
var
item
=
repository.GetById(c.id);
item.Reactivate();
}
public
void
Handle(CheckInCommand
c)
{
var
item
=
repository.GetById(c.id);
item.CheckIn(c.quantity);
}

20.
interface
Handles<T>
where
T:Command
{
void
Handle(T
command);
}

21. class
LoggingHandler<T>
:
Handles<T>
where
T:Command
{
private
readonly
Handles<T>
next;
public
LoggingHandler(Handles<T>
next)
{
this.next
=
next;
}
public
void
Handle(T
command)
{
myLoggingFramework.Log(command);
next.Handle(command);
}
}
var
handler
=
new
LoggingHandler<DeactivateCommand>(
new
DeactivateCommandHandler(...)
);

23. public
class
DeactivateInventoryItem
:Handles<DeactivateCommand>
{
private
readonly
ItemRepository
repository;
public
DeactivateInventoryItem(ItemRepository
repository)
{
this.repository
=
repository;
}
public
void
Handle(DeactivateCommand
command)
{
var
item
=
repository.GetById(command.id);
item.Deactivate(cmd.Reason);
}
}

24. public
class
DeactivateInventoryItem
:Handles<DeactivateCommand>
{
private
readonly
ItemRepository
repository;
public
DeactivateInventoryItem(ItemRepository
repository)
{
this.repository
=
repository;
}
public
void
Handle(DeactivateCommand
command)
{
var
item
=
repository.GetById(command.id);
item.Deactivate(cmd.Reason);
}
}

25. class
Handlers
{
public
static
void
Handle(ItemRepository
repository,
DeactivateCommand
c)
{
var
item
=
repository.GetById(c.id);
item.Deactivate();
}
public
static
void
Handle(ItemRepository
repository,
ReactivateCommand
c)
{
var
item
=
repository.GetById(c.id);
item.Deactivate();
}
public
static
void
Handle(ItemRepository
repository,
CheckInCommand
c)
{
var
item
=
repository.GetById(c.id);
item.Deactivate();
}

26. Back
to
the
same
problem!

27. public
static
int
Add(int
a,
int
b)
{
return
a
+
b;
}

28. public
static
int
Add(int
a,
int
b)
{
return
a
+
b;
}
var
add5
=
x
=>
Add(5,
x);

29. public
static
void
Deactivate(ItemRepository
repository,
DeactivateCommand
c)
{
var
item
=
repository.GetById(c.id);
item.Deactivate();
}

30. public
static
void
Deactivate(ItemRepository
repository,
DeactivateCommand
c)
{
var
item
=
repository.GetById(c.id);
item.Deactivate();
}
var
nodepends
=
x
=>
Deactivate(new
ItemRepository(),
x);

31.
void
BootStrap()
{
handlers.Add(x
=>
Deactivate(new
ItemRepository(),
x));
handlers.Add(x
=>
Reactivate(new
ItemRepository(),
x));
handlers.Add(x
=>
CheckIn(new
ItemRepository(),
new
BarService(),
x));
}

32.
void
BootStrap()
{
handlers.Add(x
=>
Deactivate(()
=>
new
ItemRepository(),
x));
handlers.Add(x
=>
Reactivate(()
=>
new
ItemRepository(),
x));
handlers.Add(x
=>
CheckIn(()
=>
new
ItemRepository(),
new
BarService(),
x));
}

33.
public
static
void
Log<T>(T
command,
Action<T>
next)
where
T:Command
{
myLoggingFramework.Log(command);
next(command);
}

34. class
LoggingHandler<T>
:
Handles<T>
where
T:Command
{
private
readonly
Handles<T>
next;
public
LoggingHandler(Handles<T>
next)
{
this.next
=
next;
}
public
void
Handle(T
command)
{
myLoggingFramework.Log(command);
next.Handle(command);
}
}
var
handler
=
new
LoggingHandler<DeactivateCommand>(
new
DeactivateCommandHandler(...)
);

35. <bean
id="moreComplexObject"
class="example.ComplexObject">
<!-­‐-­‐
results
in
a
setAdminEmails(java.uNl.ProperNes)
call
-­‐-­‐>
<property
name="adminEmails">
<props>
<prop
key="administrator">administrator@example.org</prop>
<prop
key="support">support@example.org</prop>
<prop
key="development">development@example.org</prop>
</props>
</property>
<!-­‐-­‐
results
in
a
setSomeList(java.uNl.List)
call
-­‐-­‐>
<property
name="someList">
<list>
<value>a
list
element
followed
by
a
reference</value>
<ref
bean="myDataSource"
/>
</list>
</property>
<!-­‐-­‐
results
in
a
setSomeMap(java.uNl.Map)
call
-­‐-­‐>
<property
name="someMap">
<map>
<entry
key="an
entry"
value="just
some
string"/>
<entry
key
="a
ref"
value-­‐ref="myDataSource"/>
</map>

36.
public
static
void
Log<T>(T
command,
Action<T>
next)
where
T:Command
{
myLoggingFramework.Log(command);
next(command);
}

37. Understand
the
problem
a
tool
or
idea
solves
well

38. If
you
need
to
add
stuff
to
your
IDE
you
are
probably
on
the
wrong
path.

39. You
own
all
code
in
your
project.
Your
boss
doesn’t
care
if
the
bug
happened
in
someone
else’s
library!