<s>
In	O
class-based	B-Application
programming	I-Application
,	O
the	O
factory	B-Language
method	I-Language
pattern	I-Language
is	O
a	O
creational	O
pattern	O
that	O
uses	O
factory	B-Language
methods	I-Language
to	O
deal	O
with	O
the	O
problem	O
of	O
creating	O
objects	O
without	O
having	O
to	O
specify	O
the	O
exact	O
class	O
of	O
the	O
object	O
that	O
will	O
be	O
created	O
.	O
</s>
<s>
This	O
is	O
done	O
by	O
creating	O
objects	O
by	O
calling	O
a	O
factory	B-Language
method	I-Language
—	O
either	O
specified	O
in	O
an	O
interface	B-Application
and	O
implemented	O
by	O
child	O
classes	O
,	O
or	O
implemented	O
in	O
a	O
base	O
class	O
and	O
optionally	O
overridden	B-Language
by	O
derived	O
classes	O
—	O
rather	O
than	O
by	O
calling	O
a	O
constructor	O
.	O
</s>
<s>
The	O
Factory	B-Language
Method	I-Language
design	O
pattern	O
solves	O
problems	O
like	O
:	O
</s>
<s>
The	O
Factory	B-Language
Method	I-Language
design	O
pattern	O
describes	O
how	O
to	O
solve	O
such	O
problems	O
:	O
</s>
<s>
Define	O
a	O
separate	O
operation	O
(	O
factory	B-Language
method	I-Language
)	O
for	O
creating	O
an	O
object	O
.	O
</s>
<s>
Create	O
an	O
object	O
by	O
calling	O
a	O
factory	B-Language
method	I-Language
.	O
</s>
<s>
See	O
also	O
the	O
UML	B-Language
class	O
diagram	O
below	O
.	O
</s>
<s>
"	O
Define	O
an	O
interface	B-Application
for	O
creating	O
an	O
object	O
,	O
but	O
let	O
subclasses	O
decide	O
which	O
class	O
to	O
instantiate	O
.	O
</s>
<s>
The	O
Factory	B-Language
method	I-Language
lets	O
a	O
class	O
defer	O
instantiation	O
it	O
uses	O
to	O
subclasses.	O
"	O
</s>
<s>
The	O
factory	B-Language
method	I-Language
design	O
pattern	O
handles	O
these	O
problems	O
by	O
defining	O
a	O
separate	O
method	B-Language
for	O
creating	O
the	O
objects	O
,	O
which	O
subclasses	O
can	O
then	O
override	B-Language
to	O
specify	O
the	O
derived	O
type	O
of	O
product	O
that	O
will	O
be	O
created	O
.	O
</s>
<s>
The	O
factory	B-Language
method	I-Language
pattern	I-Language
relies	O
on	O
inheritance	O
,	O
as	O
object	O
creation	O
is	O
delegated	O
to	O
subclasses	O
that	O
implement	O
the	O
factory	B-Language
method	I-Language
to	O
create	O
objects	O
.	O
</s>
<s>
As	O
shown	O
in	O
the	O
C#	B-Application
example	O
below	O
,	O
the	O
factory	B-Language
method	I-Language
pattern	I-Language
can	O
also	O
rely	O
on	O
an	O
Interface	B-Application
-	O
in	O
this	O
case	O
IPerson	O
-	O
to	O
be	O
implemented	O
.	O
</s>
<s>
In	O
the	O
above	O
UML	B-Language
class	O
diagram	O
,	O
</s>
<s>
MazeGame	O
declares	O
the	O
abstract	B-Language
factory	I-Language
method	I-Language
to	O
produce	O
such	O
a	O
base	O
product	O
.	O
</s>
<s>
MagicMazeGame	O
and	O
OrdinaryMazeGame	O
are	O
subclasses	O
of	O
MazeGame	O
implementing	O
the	O
factory	B-Language
method	I-Language
producing	O
the	O
final	O
products	O
.	O
</s>
<s>
Thus	O
factory	B-Language
methods	I-Language
decouple	O
callers	O
(	O
MazeGame	O
)	O
from	O
the	O
implementation	O
of	O
the	O
concrete	O
classes	O
.	O
</s>
<s>
In	O
the	O
above	O
code	O
you	O
can	O
see	O
the	O
creation	O
of	O
one	O
interface	B-Application
called	O
IPerson	O
and	O
two	O
implementations	O
called	O
Villager	O
and	O
CityPerson	O
.	O
</s>
<s>
Based	O
on	O
the	O
type	O
passed	O
into	O
the	O
Factory	O
object	O
,	O
we	O
are	O
returning	O
the	O
original	O
concrete	O
object	O
as	O
the	O
interface	B-Application
IPerson	O
.	O
</s>
<s>
A	O
factory	B-Language
method	I-Language
is	O
just	O
an	O
addition	O
to	O
Factory	B-Language
class	I-Language
.	O
</s>
<s>
You	O
might	O
also	O
write	O
your	O
custom	O
logic	O
after	O
getting	O
the	O
object	O
in	O
the	O
concrete	O
Factory	B-Language
Method	I-Language
.	O
</s>
<s>
The	O
GetObject	O
is	O
made	O
abstract	O
in	O
the	O
Factory	O
interface	B-Application
.	O
</s>
<s>
This	O
Java	B-Language
example	O
is	O
similar	O
to	O
one	O
in	O
the	O
book	O
Design	O
Patterns	O
.	O
</s>
<s>
The	O
regular	O
game	O
mode	O
could	O
use	O
this	O
template	O
method	B-Language
:	O
</s>
<s>
In	O
the	O
above	O
snippet	O
,	O
the	O
MazeGame	O
constructor	O
is	O
a	O
template	O
method	B-Language
that	O
makes	O
some	O
common	O
logic	O
.	O
</s>
<s>
It	O
refers	O
to	O
the	O
makeRoom	O
factory	B-Language
method	I-Language
that	O
encapsulates	O
the	O
creation	O
of	O
rooms	O
such	O
that	O
other	O
rooms	O
can	O
be	O
used	O
in	O
a	O
subclass	O
.	O
</s>
<s>
To	O
implement	O
the	O
other	O
game	O
mode	O
that	O
has	O
magic	O
rooms	O
,	O
it	O
suffices	O
to	O
override	B-Language
the	O
makeRoom	O
method	B-Language
:	O
</s>
<s>
Another	O
example	O
in	O
PHP	B-Application
follows	O
,	O
this	O
time	O
using	O
interface	B-Application
implementations	O
as	O
opposed	O
to	O
subclassing	O
(	O
however	O
,	O
the	O
same	O
can	O
be	O
achieved	O
through	O
subclassing	O
)	O
.	O
</s>
<s>
It	O
is	O
important	O
to	O
note	O
that	O
the	O
factory	B-Language
method	I-Language
can	O
also	O
be	O
defined	O
as	O
public	O
and	O
called	O
directly	O
by	O
the	O
client	O
code	O
(	O
in	O
contrast	O
with	O
the	O
Java	B-Language
example	O
above	O
)	O
.	O
</s>
<s>
Same	O
as	O
Java	B-Language
example	O
.	O
</s>
<s>
In	O
ADO.NET	B-Device
,	O
is	O
an	O
example	O
of	O
the	O
use	O
of	O
factory	B-Language
method	I-Language
to	O
connect	O
parallel	O
class	O
hierarchies	O
.	O
</s>
<s>
In	O
Qt	B-Language
,	O
is	O
a	O
factory	B-Language
method	I-Language
declared	O
in	O
a	O
framework	O
that	O
can	O
be	O
overridden	B-Language
in	O
application	O
code	O
.	O
</s>
<s>
In	O
Java	B-Language
,	O
several	O
factories	O
are	O
used	O
in	O
the	O
package	O
.	O
</s>
<s>
javax.xml.parsers.DocumentBuilderFactory	O
or	O
javax.xml.parsers.SAXParserFactory	O
.	O
</s>
<s>
In	O
the	O
HTML5	B-Application
DOM	B-General_Concept
API	I-General_Concept
,	O
the	O
Document	O
interface	B-Application
contains	O
a	O
createElement	O
factory	B-Language
method	I-Language
for	O
creating	O
specific	O
elements	O
of	O
the	O
HTMLElement	O
interface	B-Application
.	O
</s>
