00:00:07.600
glad to be here glad to be open in the
00:00:09.960
track and
00:00:12.040
uh I'm going to like for the this year I
00:00:16.800
love to talk about service subjects I
00:00:19.560
spent a lot of time thinking about them
00:00:22.560
and uh thinking about how to think about
00:00:25.720
them so I'm going to be sharing some of
00:00:28.000
the some of my learnings
00:00:31.360
uh a little bit about myself I'm on rail
00:00:35.320
since 2006 so it might tell you
00:00:37.399
something about my age I my current role
00:00:40.160
is CTO at cle.com where we help
00:00:42.760
companies manage their assets and
00:00:44.879
licenses and do it in an easy way my
00:00:48.039
passion is complexity organization
00:00:50.199
optimization so that not that I only
00:00:53.039
love to organize complexity I love to do
00:00:56.399
it in an optimal way so and uh my
00:01:00.640
consultancy called rbbr limited we help
00:01:04.199
small to medium startups to grow their
00:01:06.920
codebase uh so that they don't lose
00:01:09.920
scalability over time and my methodology
00:01:13.320
is painless rails uh it's not too
00:01:16.720
popular yet I hope it's one day it's
00:01:19.000
going to get a bit more popular a few
00:01:21.880
links below feel free to visit them to
00:01:26.119
follow me and read more about my stuff
00:01:29.479
and
00:01:31.680
what I want to say is Service uh like
00:01:35.000
service object is a fake concept this is
00:01:38.240
my statement but service objects
00:01:41.360
nowadays they are a the facto standard
00:01:44.920
of uh a standard way to organize
00:01:48.040
complexity in rails
00:01:49.960
applications and still I do think
00:01:53.320
so and this year I give one hour talk
00:01:58.479
about the curse of Serv objects in
00:02:01.600
Poland in brl and
00:02:05.119
uh today I decided to reshape my talk
00:02:08.879
because first of all it's 30 minutes and
00:02:11.400
second thing I decided to focus on one
00:02:14.000
thing the shape of a service object but
00:02:17.560
to talk about the shape of service
00:02:19.120
object we first uh I I first need to
00:02:21.720
tell you about one thing I invented uh
00:02:24.480
several years ago that was mostly a joke
00:02:27.959
a funny thing to do but uh I call it
00:02:32.080
code topology notation and these days I
00:02:34.720
find it more and more useful and as well
00:02:37.599
as in discussions about architecture
00:02:40.159
about software decisions and
00:02:44.040
uh uh also on a day-to-day job as well
00:02:47.400
to kind of model things and try out so
00:02:51.120
the
00:02:51.920
notation the basic idea there is to
00:02:56.239
display uh objects as little dummies
00:03:00.519
and their hands
00:03:03.239
are uh represent
00:03:05.519
methods so kind of in order to invoke a
00:03:09.440
method you shake uh a guy's
00:03:12.879
hand and if if you take a closer look
00:03:16.400
you might realize that fingers actually
00:03:18.480
represent arguments so the more uh
00:03:21.480
arguments the more fingers but they kind
00:03:24.440
of not a normal fingers but Robo fingers
00:03:27.519
like robot tube fingers so they can
00:03:29.480
access arguments from outside and maybe
00:03:32.360
store them for late resarch in some
00:03:35.280
other
00:03:36.159
methods so I hope you're still with me
00:03:40.239
and to return the method there's a hatch
00:03:42.799
on the belly that which opens and you
00:03:44.959
can grab a result there and also private
00:03:49.400
methods my my favorite concept those are
00:03:52.920
kind of internal hands which only the
00:03:55.799
guy himself can shake uh but no one from
00:03:59.280
from out it
00:04:00.799
can and there's more to it but like the
00:04:06.040
the only the the One More Concept we
00:04:08.840
need is a class and a class is a kind of
00:04:11.680
spawning platform with instructions what
00:04:14.680
object to spawn and there's a lever and
00:04:17.359
you pull this
00:04:18.680
lever and you get an object and of
00:04:22.840
course you can get as many objects as
00:04:24.600
you
00:04:25.520
need and uh what is interesting is that
00:04:29.720
that essentially both objects and
00:04:32.039
classes they have the same topology
00:04:34.639
because lever could actually have
00:04:37.039
arguments could actually have fingers
00:04:40.320
and it's the same thing as a hand and
00:04:43.039
the same with a hand it can have no
00:04:45.400
fingers no
00:04:47.360
arguments so and one example of uh
00:04:52.320
application of this topology is that you
00:04:54.800
can first of all you can reflect
00:04:57.840
complexity of your code by simply
00:05:01.320
expressing um by simply drawing those
00:05:03.960
little dummies and their arms and how it
00:05:06.680
looks like and uh here you can see how
00:05:10.360
complexity grew over time uh when code
00:05:14.720
was uh getting more and more complex so
00:05:18.560
this is exactly how are we going to talk
00:05:20.759
about the shape of service objects I did
00:05:24.360
small research recently and um
00:05:30.520
I was looking for how developers um
00:05:34.840
think what they think service objects
00:05:37.680
are what they useful for and how they
00:05:39.800
look and I'm going to quickly show few
00:05:43.080
examples of service objects I I found on
00:05:46.680
internet and um uh on the right you can
00:05:51.520
see their shape in our code topology
00:05:54.600
notation so this guy is simply a wrapper
00:05:58.240
around Twitter API
00:06:00.199
and you see like we have a Constructor
00:06:02.400
with one argument and we have one public
00:06:05.639
method um here we have a Book Creator
00:06:09.120
service object called Book Creator again
00:06:11.120
we have a Constructor with four
00:06:13.639
arguments um public method uh can accept
00:06:17.960
any number of arguments so we have this
00:06:20.440
kind of funnel instead of fingers and we
00:06:23.240
also have one uh private method uh which
00:06:26.560
you can
00:06:27.400
see uh there
00:06:30.680
again like few more
00:06:33.000
examples and you can see they kind
00:06:36.560
of like the
00:06:39.360
code might look a bit strange for some
00:06:41.960
of you like this example for example it
00:06:44.120
does some validation for for some reason
00:06:46.240
it's still a service this one it just
00:06:48.840
does simple calculation in one line and
00:06:51.039
it's still a separate class and a
00:06:53.440
separate object but
00:06:55.879
anyway um so and there are also
00:06:59.960
like this this example is a little bit
00:07:01.520
more complex there are four private
00:07:03.879
methods but if we try at this stage look
00:07:07.080
at adjust this samples of code if we try
00:07:10.440
to derive an idea of service object out
00:07:12.800
of
00:07:13.520
it the definition would be pretty much
00:07:16.080
it they just do
00:07:17.840
stuff and they all looks the same they
00:07:21.240
they share the shape so the shape would
00:07:24.280
be okay there's a
00:07:26.360
Constructor uh it it usually accepts
00:07:29.360
some arguments there's a public method
00:07:31.280
with no arguments and there could be a
00:07:33.919
number of uh private
00:07:38.720
methods and serious guys are doing it
00:07:41.680
too I'm going to show you this
00:07:45.879
uh example of a service object from
00:07:49.280
gitlab from the codebase of gitlab and
00:07:52.440
it is uh the code is around 200 lines of
00:07:56.919
code and
00:08:00.039
I'm going to show you how how it looks
00:08:02.319
in in this notation it looks like
00:08:06.639
this so but what's what's
00:08:10.120
interesting is that at the beginning it
00:08:12.520
actually looked not too scary so I look
00:08:16.639
at the history of of those changes and
00:08:18.560
in the beginning it it looked exactly
00:08:20.919
like we seen
00:08:22.400
in the start of my
00:08:25.720
talk
00:08:27.599
so and
00:08:31.319
yeah it looks like over time if you do s
00:08:34.479
if you do practice service
00:08:36.240
objects if a certain area of your
00:08:40.120
project will be uh will become more
00:08:42.800
complex the complexity will grow
00:08:45.720
Inward and for me it doesn't look like
00:08:48.720
an optimal way to organize
00:08:50.920
complexity and let me show you how I
00:08:54.519
would do it so my
00:08:58.120
methodology I think there are three
00:09:00.240
pillars three main principles like first
00:09:03.079
of
00:09:04.040
all please do practice layered
00:09:07.360
architecture please make sure your
00:09:09.200
obstructions are of a single level of
00:09:12.120
obstruction so that they don't kind of
00:09:14.800
Jump Around multiple layers
00:09:18.079
and around multiple levels of of
00:09:22.079
obstructions and the third one this is
00:09:24.760
the one which we're going to be focusing
00:09:27.079
on I and if if you like if you haven't
00:09:31.920
been listening to me at all and you will
00:09:34.959
remember only one thing after my talk I
00:09:37.240
want you to remember this thing so think
00:09:39.920
about this idea splitting code
00:09:43.120
into uh into different building blocks
00:09:46.399
by the types of work this code is doing
00:09:49.720
and let me show show you what I mean we
00:09:51.880
will take this service object which is
00:09:54.959
not too big like gitlabs which is
00:09:57.320
already not too small and there are
00:10:00.200
like we can already start considering a
00:10:03.320
refactor inovate or at least we can
00:10:05.880
easily demonstrate the idea of types of
00:10:07.959
work here
00:10:11.760
so I'm not sure if you if you can see it
00:10:15.040
but um below like uh what what this code
00:10:20.600
does it calls um it sends an email so it
00:10:24.079
uses some external service and um you
00:10:28.839
can see here I kind of highlight arms of
00:10:33.000
of this guy to represent um where this
00:10:37.920
type of work um is
00:10:40.279
located
00:10:42.600
so here we can see mutations so we do
00:10:46.079
mutate do some changes in the database
00:10:49.279
and this logic is spread across two
00:10:51.480
private
00:10:53.440
methods uh this one is what I call
00:10:56.399
business rule it is where we ask a user
00:11:00.399
about something about not about
00:11:02.279
something about himself I mean user
00:11:05.399
entity and again this logic is spread
00:11:08.279
across two private methods and we can
00:11:10.839
also see that uh service object
00:11:15.279
also works to some extent as a
00:11:18.079
controller at least it has a notion of
00:11:20.320
session it of JWT talking uh it has a
00:11:25.120
notion of rendering at least It prepares
00:11:27.880
success or result and
00:11:30.000
response so yeah we can see that here
00:11:35.360
the guys take care about all those types
00:11:37.959
of works and let's see what's going to
00:11:40.320
happen when we um try to rearrange it so
00:11:45.480
that each type of work is done within
00:11:48.600
its in its own building block let's find
00:11:51.760
its own shelf for every type of work
00:11:53.800
being done here so first of all let's
00:11:58.120
extract
00:11:59.760
business rules and luckily in rails we
00:12:04.040
kind of already have a proper shelf for
00:12:07.000
for business rules if we ask
00:12:09.519
user uh about himself let's maybe just
00:12:12.680
move it to a user
00:12:14.079
model and yeah that's the code that's
00:12:18.760
the shape of our user we just added two
00:12:20.720
methods to a user
00:12:22.839
model okay next
00:12:25.680
step uh mutations
00:12:29.480
and this might be a not not very obvious
00:12:33.680
move um what I do here
00:12:38.880
I I introduce a concept of mutators and
00:12:42.639
those mutators are just functions
00:12:46.800
and I just move all the logic all all
00:12:51.079
the creation logic all the update logic
00:12:53.600
in one single procedure so it's not the
00:12:57.760
logic is is not getting
00:13:00.600
um um split across multiple models in
00:13:05.440
callbox for example it is all in one
00:13:07.639
method it's explicitly uh it is an
00:13:10.279
explicit procedure so
00:13:13.279
and module I use just as a container for
00:13:16.600
those functions I call it user module I
00:13:19.920
call it user mutator but the actual
00:13:22.920
mutators are functions so um yeah we
00:13:27.040
introduce basically two functions here
00:13:30.120
um next move let's extract all the
00:13:33.920
controller Logics back to the controller
00:13:36.800
so that because before that our service
00:13:41.279
object was working as a controller and I
00:13:44.600
assumed that uh controller was just
00:13:47.160
calling this uh service object and it
00:13:49.519
was mostly
00:13:51.079
empty so it was maybe too
00:13:54.360
skinny okay so we just uh moved some
00:13:57.040
logic to controller and we like
00:13:59.880
obviously we already had this had this
00:14:02.079
thing uh we just modified uh the create
00:14:05.639
uh
00:14:08.320
action okay and once we moved everything
00:14:12.079
out let's see what's left in our service
00:14:15.759
and
00:14:16.560
again
00:14:18.920
um again it's just a function or more
00:14:23.399
correct
00:14:24.519
procedure again it is located within a
00:14:27.680
module but it could be class as well
00:14:29.759
because the top topology is the same I'm
00:14:31.720
not creating any objects here it's just
00:14:35.279
a method which accepts three arguments
00:14:38.600
and does its
00:14:39.839
job and you can see that um it calls
00:14:44.560
user it calls some method methods from
00:14:46.959
user model it calls it asks to do some
00:14:50.480
job for user mutators and it calls um uh
00:14:56.120
it involves a method in a user mailer so
00:14:59.360
instead of us having like a big piece of
00:15:02.639
code doing lots of different types of
00:15:05.839
low-level work we now have a
00:15:09.759
highlevel code which uh we fit in a
00:15:13.839
single function so this is what we did
00:15:17.320
essentially this is what we had and this
00:15:20.120
is what we've got so we introduced five
00:15:23.680
methods we modified uh a control
00:15:26.079
diretion uh two methods went to uh to a
00:15:29.319
model and we introduced three me methods
00:15:32.240
and we
00:15:33.319
found
00:15:35.040
uh kind of building blocks for them
00:15:37.720
which
00:15:38.560
are simply containers of uh of
00:15:46.759
functions so here you can see how we uh
00:15:50.480
distributed all the types of work across
00:15:52.959
different building
00:15:54.240
blocks and
00:15:57.160
uh interestingly
00:15:59.839
if we try to uh draw how it's how it's
00:16:04.560
used it looks like uh our user is
00:16:07.920
getting used by user
00:16:09.920
mutator
00:16:11.759
our uh service uses uh mutator and it
00:16:16.600
can use model as well and controller can
00:16:20.120
use uh any of them basically so and it
00:16:23.839
will be very strange in this
00:16:26.000
architecture if you would try to use a
00:16:28.279
service from my mutator it's not what
00:16:30.759
you expect here and
00:16:35.279
basically you can easily spot that if
00:16:37.680
you prefer isolated testing this setup
00:16:40.560
would be much easier to
00:16:42.279
test also this is what we call
00:16:46.120
modularity and this is what we call
00:16:48.079
layered
00:16:49.759
architecture and I want to remind you
00:16:52.920
that
00:16:53.920
rails is supposed to be a layered
00:16:56.800
architecture just that they were just
00:16:58.959
two layers models and controllers and
00:17:01.759
with the idea of service objects we
00:17:03.839
actually what we wanted to do is to
00:17:05.520
actually introduce another layer kind
00:17:07.720
service
00:17:08.679
layer but uh I think as a community we
00:17:12.880
failed and essentially we have no layers
00:17:15.559
anymore and but this is what we've got
00:17:19.360
with mutators and with services this is
00:17:21.839
the architecture what we've got like uh
00:17:24.240
in the core we have our Primitives our
00:17:26.079
entities models then we have mutators
00:17:28.679
who who can operate with our entities
00:17:31.679
there are and then there are more high
00:17:33.440
level obstructions like Services which
00:17:35.960
represent business operations in my code
00:17:39.160
and they are kind of smarter things they
00:17:41.080
can operate with mutators and models and
00:17:43.840
controllers like they uh manipulate all
00:17:46.720
the things below so but one could say
00:17:51.440
wait we could still while refactoring
00:17:54.520
that service object we could still uh
00:17:57.200
put those kind of
00:17:59.400
we could still use service objects for
00:18:01.360
those types of work right and let's do
00:18:05.360
this so this is the code which I put
00:18:08.760
like two methods to a user model uh I
00:18:11.760
extracted let's put them in a separate
00:18:14.120
service object instead of doing this so
00:18:17.039
I create a class called user business
00:18:19.799
rules and there's a Constructor and
00:18:23.080
there are two public methods which
00:18:25.679
actually give us answer about this user
00:18:31.960
um user um user
00:18:37.120
mutator uh we turn it into two service
00:18:40.120
objects with the names login event
00:18:43.320
recorder and failed login
00:18:45.840
Handler and yeah we've got two of these
00:18:49.400
little dummies here and service yeah we
00:18:53.200
we also turn it into a service
00:18:55.280
object and this is what we've got
00:18:59.159
so on the black part this is amount this
00:19:02.880
is how our topology how topology of our
00:19:07.039
code looks like with the idea of with
00:19:09.679
the just idea uh of types of
00:19:13.120
work and with with this idea plus the
00:19:17.360
idea of service objects we get this
00:19:19.240
amount of complexity so we get
00:19:23.600
um I would say we have uh we we get a
00:19:27.039
decent amount of accidental complexity
00:19:29.840
here and this is what I mean this is
00:19:33.640
what I mean by finding an optimal way to
00:19:36.919
organize complexity so on the left this
00:19:40.400
is what we had before refactoring and
00:19:44.159
this is and this we don't like because
00:19:46.559
complexity would grow Inward and we we
00:19:48.799
will get infinite number of private
00:19:51.039
methods uh and on the right this is what
00:19:53.960
I would get if I would be keep using
00:19:56.520
service object even if I don't have to
00:20:01.039
so and this is how it's going to look
00:20:03.919
like uh on a scale so this is
00:20:08.600
how uh some of my shelves for building
00:20:12.640
blocks for different types of work look
00:20:15.440
like so I have Services I have mutators
00:20:18.559
I have managers managers in my code are
00:20:21.280
just wrappers around um external
00:20:24.440
Services I have forms I have business
00:20:26.960
rules they go just as a method to my
00:20:32.880
models and yeah um I get this layered
00:20:38.360
architecture and at this point I would
00:20:41.720
Reen I would like to rename my talk and
00:20:44.640
new name of my talk would be the shape
00:20:47.640
and the missing idea of a service object
00:20:50.760
because at this point I
00:20:53.320
think uh there is
00:20:56.240
no idea there is no philosophy ophy um
00:21:00.640
um in service object I think the only
00:21:03.840
idea of a service object is its
00:21:07.120
shape and what
00:21:09.840
I very much dislike about this is that
00:21:13.559
it makes you focus on a wrong thing it
00:21:17.240
makes you focus on an empty concept
00:21:20.120
instead of really organizing your code
00:21:23.080
you're just focus on the
00:21:26.279
shape and this is what we get
00:21:29.240
so we just
00:21:30.679
get a very very different um service
00:21:35.440
object which either uh do different
00:21:39.320
types of work and they are put into the
00:21:42.679
same bucket or
00:21:46.000
Worse um inside service object they do
00:21:49.480
all the different types of work and they
00:21:51.720
still put in the same bucket and this
00:21:54.919
bucket like is located um
00:21:59.120
it's it's located nowhere and
00:22:02.640
everywhere because um it it
00:22:08.360
steals all the responsibilities from
00:22:10.720
controllers layers and all the
00:22:12.720
responsibilities from the model layer
00:22:14.480
and it it it does everything basically
00:22:17.320
so with this idea we effectively kill uh
00:22:22.200
uh lay
00:22:24.039
architecture and one more
00:22:27.200
thing I want want to
00:22:30.520
share like not only I did some research
00:22:33.520
about um about how developers do service
00:22:37.240
object I also tried to find how like
00:22:41.400
smart people who were thinking about it
00:22:43.760
like years before in this example fer
00:22:46.960
and Evans what they were saying about
00:22:50.159
service objects and surprisingly they
00:22:53.120
didn't say a thing so but what they said
00:22:56.520
about fer mentioned mentioned an idea of
00:23:00.240
service layer and Evans mentioned domain
00:23:03.640
services and I'm not going to
00:23:06.799
um share the whole
00:23:09.159
story but what I did basically I um
00:23:13.159
represented visually what they were
00:23:15.520
saying
00:23:17.320
and this you will be able to see in
00:23:20.400
details in my presentation which I going
00:23:22.640
to share in the end of my
00:23:24.640
talk and Evans ideas they look
00:23:28.960
like this what I wanted to share here is
00:23:32.600
that I took their
00:23:35.520
ideas and I kind of decided to make it
00:23:38.880
more compact I assume they were talking
00:23:41.799
about the same idea because it looks
00:23:44.159
like it and I kind of compressed they
00:23:47.520
what they were saying
00:23:49.480
about and this is what they were saying
00:23:52.279
about so they're saying that domain
00:23:56.159
service is stateless it is named for an
00:23:59.279
activity not entity it represents
00:24:01.279
business operation so some calculation
00:24:04.679
not some random calculation is not a
00:24:07.720
business operation a rapper around uh
00:24:11.240
rest API is not a business
00:24:13.400
operation it coordinates the main
00:24:15.640
objects it controls
00:24:17.799
transactions uh it should theoretically
00:24:20.039
have side effects it could happen that
00:24:22.559
there will be no side effect because
00:24:24.240
some some if condition but theoretically
00:24:27.840
there like it there should be a side
00:24:29.760
effect and there should be no
00:24:31.159
application logic because Evans
00:24:33.840
specifically he draws a line between
00:24:36.600
domain services and Technical Services
00:24:38.960
and he says those are not the same those
00:24:41.000
are different things
00:24:43.279
so and what we what we've got here is
00:24:47.200
that we actually crafted a ruler here
00:24:50.679
and we can take every service around we
00:24:54.000
can uh grab any service object and we
00:24:57.159
can measure with this follow Evans ruler
00:25:00.600
and see like uh to what extent it
00:25:04.760
matches what they were
00:25:06.399
saying
00:25:09.080
and the good news is that I actually um
00:25:13.640
I made a custom chart
00:25:15.279
GPT where you can put your code and it
00:25:19.200
will tell you how much uh how many
00:25:21.799
points it gets according to this ruler
00:25:25.679
and if you get five out of s most
00:25:29.880
probably you're using service service
00:25:32.760
object where you don't have two where
00:25:35.240
function will be enough I recommend you
00:25:38.120
to play with it uh it's going it is fun
00:25:42.360
and my general
00:25:46.000
recommendations don't use the term
00:25:48.039
service object because again it's an
00:25:50.200
empty concept it's an empty abstraction
00:25:52.559
there is no deep philosophical idea
00:25:55.840
behind it uh second recommendation don't
00:25:59.360
use service
00:26:01.200
objects um you still can but you if you
00:26:05.679
do you should be ready to answer the
00:26:08.320
question what is your personal idea
00:26:10.760
behind it so you can still use it as a
00:26:14.840
like as a technical trick if you find it
00:26:17.320
useful I don't find it useful I find it
00:26:21.760
confusing um and types of work of your
00:26:26.559
your code is doing is essentially type
00:26:28.399
of building block you have in your
00:26:30.720
applications and um and yeah do try to
00:26:34.679
measure your services with fer evance
00:26:37.240
ruler
00:26:39.000
and the good news is that all this stuff
00:26:43.320
uh is pretty easy to find just go to
00:26:46.120
rails. Services there I put my uh
00:26:49.880
presentation there I put uh some links
00:26:53.320
from the talk there I put the link for
00:26:55.919
this fer evance ruler and and there you
00:26:58.799
can find the recording of my talk in
00:27:00.640
Poland one hour long where I was talking
00:27:03.559
about all this in much more details
00:27:06.960
thank
00:27:17.720
you and one thing I do uh if you
00:27:22.760
disagree with me please find me and talk
00:27:26.320
to me I would love to for you to explain
00:27:28.679
me why service objects is a good idea
00:27:31.120
maybe I'm still missing something I
00:27:33.399
would love you to to tell me that thank
00:27:35.559
you
