Interfaces vs Abstract Classes
Summary
TLDRThis video script delves into the nuances of abstract classes and interfaces, contrasting their syntactical differences and use cases. It highlights that while both cannot be instantiated and can contain static members, they serve different purposes in code design. Abstract classes encapsulate commonality among related entities, whereas interfaces decouple components, enhancing flexibility. The script uses analogies like shapes and vehicles to illustrate concepts and discusses scenarios where one might be favored over the other, emphasizing the trade-offs between inheritance and composition in structuring code for maintainability and flexibility.
Takeaways
- 📜 Abstract classes and interfaces are common interview topics and are used to encapsulate common behaviors or roles in code.
- 🔍 The syntactical difference lies in that interfaces can only have public methods and properties, while abstract classes allow for various access modifiers and constructors.
- 🚫 Neither abstract classes nor interfaces can be instantiated directly.
- 🔗 A class can implement multiple interfaces but can only inherit from one abstract class due to the concept of identity.
- 🎯 Abstract classes are used when there is a commonality among classes, while interfaces are chosen for their role in decoupling components and increasing flexibility.
- 📈 Interfaces can provide scope control and enable immutability, whereas abstract classes cannot offer this level of control.
- 🏗️ Traits or roles, a programming paradigm, can be implemented using interfaces but not abstract classes, as a class can play multiple roles through interfaces.
- 🔄 In scenarios where additional responsibilities are anticipated, abstract classes might be more suitable than interfaces.
- 🔧 Inheritance leads to succinct code but may limit reusability, whereas composition with interfaces allows for greater flexibility but can increase code volume.
- 🔎 The choice between inheritance and composition depends on the specific needs of the project, with composition generally preferred for its flexibility.
- 💡 Understanding the differences and appropriate use cases for abstract classes and interfaces is crucial for writing maintainable and flexible code.
Q & A
What is the primary purpose of discussing abstract classes and interfaces in the context of the video?
-The primary purpose is to clarify the syntactical differences, use cases, and to provide examples of when to use abstract classes or interfaces in programming, especially in the context of interviews and software design decisions.
What are some key syntactical differences between abstract classes and interfaces?
-Abstract classes can have access modifiers, default implementation methods, fields, and constructors. Interfaces, on the other hand, can only have public methods, default implementation methods (but not consumed within the implementing class), and properties (but without fields).
Why might you choose to use an interface over an abstract class in a particular scenario?
-You might choose an interface when you want to introduce more flexibility into your code by decoupling components, allowing for multiple roles or behaviors to be played by a class, and when you need to maintain a contract without enforcing a specific implementation.
How do abstract classes and interfaces handle the concept of immutability and state management?
-Interfaces can be used to enforce immutability by defining properties that can only be initialized and not reinitialized, effectively controlling the state of an object. Abstract classes do not inherently support this pattern without additional implementation.
What is the significance of the shape and vehicle analogies in understanding abstract classes?
-The analogies help to illustrate that a class can represent a general concept (like a shape or a vehicle) and share common properties or behaviors with other classes within that concept, which is the essence of using an abstract class to encapsulate commonality.
How can you explain the use of default implementation methods in abstract classes versus interfaces?
-In abstract classes, default implementation methods can be consumed within the inheriting class, whereas in interfaces, the default implementation cannot be directly accessed by the implementing class; instead, the class must provide its own implementation or use the default implementation from the interface.
What is the main advantage of using composition with interfaces over inheritance with abstract classes?
-Composition with interfaces provides greater flexibility, as it allows for the decoupling of components and the ability to mix and match behaviors in different contexts. It enables reusability of interfaces across various parts of an application, whereas inheritance may lead to tightly coupled and less flexible code structures.
Why might you prefer an abstract class in a scenario where multiple context-specific behaviors are needed?
-In such scenarios, abstract classes can be used to define a common structure or behavior that is shared across different contexts, making it easier to manage and reuse the shared logic without having to implement multiple interfaces for each context-specific behavior.
What are the trade-offs between using inheritance and composition in software design?
-Inheritance provides a succinct way to express related concepts and share common logic, but it can lead to tightly coupled code that is difficult to refactor. Composition, on the other hand, offers more flexibility and decoupling but may require more code and explicit orchestration of components.
How does the video script illustrate the concept of 'scopes' in relation to interfaces?
-The concept of 'scopes' is illustrated by showing how interfaces can define a set of behaviors or properties that are accessible only within a certain scope or state of an object, providing a structured way to control access and maintain immutability.
What is the role of traits or roles in object-oriented programming, and how do interfaces support this concept?
-Traits or roles represent specific behaviors or functionalities that an object might adopt within certain contexts. Interfaces support this concept by allowing a class to implement multiple interfaces, effectively playing multiple roles, which is not possible with abstract classes that enforce a single role or identity.
Outlines
📚 Introduction to Abstract Classes and Interfaces
This paragraph introduces the topic of abstract classes and interfaces, highlighting their importance in software development interviews. It emphasizes the need to understand the syntactical differences between the two and their use cases. The speaker shares personal experience of asking this question in interviews and suggests that even those who feel confident may struggle to articulate the nuances. The paragraph sets the stage for a detailed discussion on when and why to use abstract classes or interfaces, and it invites viewers to engage by liking, subscribing, and commenting.
🔍 Exploring Analogies and Use Cases
The second paragraph delves into analogies and practical examples to better understand abstract classes and interfaces. It uses shapes and vehicles to illustrate the concepts and contrasts them with programming realities. The speaker discusses the limitations and capabilities of both abstract classes and interfaces, such as the inability to instantiate them and their potential to contain static members. The paragraph also touches on the idea of implementing multiple interfaces versus inheriting from a single abstract class, and it provides examples of scenarios where one might be preferred over the other.
🤔 Decision-Making Between Abstract Classes and Interfaces
This paragraph focuses on the decision-making process when choosing between using an abstract class or an interface. It presents a scenario where both can be used interchangeably but advises against using abstract classes when additional responsibilities can be attached to the operation. The speaker introduces the concept of 'Scopes' and 'traits' or 'roles', explaining how interfaces enable these programming paradigms, which abstract classes cannot support. The paragraph concludes with a discussion on inheritance versus composition, emphasizing the flexibility and potential code volume trade-off when using interfaces over abstract classes.
Mindmap
Keywords
💡Abstract Class
💡Interface
💡Syntactical Difference
💡Dependency Breaking
💡Composition vs. Inheritance
💡Default Implementation
💡Commonality Extraction
💡Contract
💡Decoupling
💡Identity vs. Behavior
Highlights
The video discusses the differences between abstract classes and interfaces, a popular interview question.
Abstract classes and interfaces are syntactically different, with interfaces being more restrictive in terms of access modifiers.
Interfaces can only have public methods and cannot have access modifiers specified, unlike abstract classes.
Abstract classes can have fields, constructors, and any access modifier methods, while interfaces cannot.
Both abstract classes and interfaces cannot be instantiated and can contain static members.
A class can implement multiple interfaces but can only inherit from one abstract class due to the concept of identity.
Abstract classes are used when there is a commonality among classes, while interfaces are used to break dependencies and increase flexibility.
Examples of using abstract classes include shapes like squares and circles, while interfaces can be used for vehicles or animals.
In web development, abstract classes are less commonly used compared to interfaces.
Abstract classes can be used to create a structure where operations share commonalities, like in the example of a stopwatch timing operations.
Interfaces can be used for scope control, allowing for immutability and a structured way to use code.
Traits or roles, a programming paradigm, can only be implemented with interfaces, not abstract classes.
The debate between inheritance (using abstract classes) and composition (using interfaces) is discussed, with a preference for composition in most cases.
Inheritance provides succinct code but may lead to tightly coupled components, while composition offers flexibility at the cost of increased complexity.
The video concludes with a recommendation to use interfaces and composition for their flexibility, unless a clear commonality among classes justifies an abstract class.
The presenter invites viewers to like, subscribe, and leave comments or questions for further discussion.
The source code for the examples in the video is available for patrons on Patreon.
Transcripts
welcome back boys and girls today we're
going to be talking about abstract
classes and interfaces it is a very
popular interview question and I
personally liked asking it myself as
well the interview question goes like
this you first ask to explain the
difference between an abstract class and
an interface so what is the syntactical
difference how do you use it why would
you use one over the other one and
perhaps can you give me some examples as
you go through the explanation of these
questions there are a lot of points
where you can ask the candidate to drill
down into their EXP ation and at some
points people just run out of things to
say or they just don't know what to say
even now if you're sitting there and
you're thinking I I know everything
about abstract classes and interfaces if
I actually start interviewing you about
it you may struggle to explain some
points so if you ever struggled with
articulating your thoughts on abstract
classes and interfaces the differences
between the two and why would you use
one over the other one hopefully this
video can help you don't forget if
you're enjoying the video leave a like
And subscribe if you if you have any
questions make sure to leave them in the
comment section if you think there is
anything that I have missed go ahead and
leave it in the comment section as well
I have a C Core status out if you would
like to know c as I did highly recommend
you take a look at it before we actually
start looking at the code I want to
outline a general idea for abstract
classes and interfaces so you can get a
feeling for why would you want to use
one over the other one and perhaps an
idea of their shape so for abstract
classes there is a set of things there
is then a commonality amongst all of
those things and you're taking that
commonality and extracting it into an
abstract class with interfaces you have
two parts of your code to components
where one depends on the other one and
you want to break this dependency
because you want to substitute the thing
that it's depending on or the thing that
it's consuming essentially introducing
more flexibility into your code this is
where the contract the bridge the
interface comes in ultimately used to
decouple your components in code with
this let's go ahead and get started here
I have a bunch of files we're going to
go through them one by one the first is
the abstract class over here and then
the interfaces we're going to take a
look at the difference between the two
syntactically first interfaces are a
little bit smaller so the first thing
that we can take a look at is you cannot
actually have access modifiers or you
cannot put the ones that you want you
can only put public you can make them
explicit but you can't actually specify
them with abstract classes you can put
whatever access modifier that you want
and the only thing that you can Define
on interfaces are methods either
abstract methods or just method
definitions which are the same on the
abstract class which are abstract
methods over here and then default
implementation methods you can also have
them on the abstract class however there
is a slight difference between the two
so a default implementation method on an
abstract class can be consumed within
the inheriting class so s string can be
used over here and then if I instantiate
a square I can also consume that
function on there if I'm using an
interface the space which is
implementing the interface I cannot
reach the default implementation on here
I will actually have to go to the
interface itself so here I will be able
to reach this function okay now you can
also specify properties on an interface
however that is only going to be
concerned for the methods of the
property because a property is three
parts two methods getter and Setter
depending on which ones you specify and
also a field with an abstract class you
can actually get Fields if you specify a
property on an interface you don't
actually get a field and then another
thing that an abstract class can have
that an interface cannot have is a
Constructor and that is pretty much it
for the differences between the two you
can also talk about commonalities
between the two how are abstract classes
and interfaces similar neither of them
can be instantiated they both both can
still contain static members and that's
about it now moving on to how you would
actually use an abstract class versus an
interface you implement an interface and
you inherit from an abstract class you
can Implement multiple interfaces on a
single class and then you can only
inherit from one abstract class the
reason you can only inherit from one is
because there is a notion of identity a
square is a shape a square cannot be an
animal and shape a square at that point
has schizophrenia so when we're talking
about implementing an interface it is
more do I have this Behavior am I
playing this role these are partly the
ideas that you can figure out when
you're thinking or you're talking about
implementing some kind of feature is it
a thing or do we have this Behavior May
sway you in one direction or the other
whether you should be choosing an
abstract class or an interface so that's
about it for the difference between the
two if you're wondering about the
example that I have over here it's a
shape example a square is a shape a
circle is a shape you can then have
triangles you can have other examples
such as Vehicles animals so truck
motorcycle car those are vehicles for
Animals you have red cat Etc these are
very good analogies to understand
abstract classes however when you
actually get to programming uh the
concepts vary slightly and generally in
web development you don't really get
that many opportunities to create
abstract classes like that although
there are places like video games where
if you have some kind of objects on the
plane you get a lot of options to
basically say ah I should have this
abstract class where all of the objects
have some kind of position in the game
for the interfaces I have an example of
a cache so if for example I have my
application using cash everywhere if I
want to substitute a cash at
implementation at any point going from
redis to M cach or to some kind of other
cache that is going to come out in the
in the future I don't have to change the
whole application to depend on a
different service I just substitute the
implementation for the interface and and
my application should just keep working
as it does why would you actually use an
abstract class over an interface or an
interface over an abstract class in some
cases there really is no difference
whether you use one or the other one and
Abstract classes can behave like
interfaces and this is what this example
is about I'm going to tell you what to
do in this situation for example we have
something that depicts an operation this
is really to Mark functions okay we have
an operation that is going to increment
we then have an I try so we try to
execute an operation and the operation
that we depend on is this interface we
then have an night time again we start
up a stop stopwatch and we try to time
the time it takes to execute an
operation and again we depend on this
eye operation we then have the
individual permutations where we compose
things together now with abstract
classes you can effectively arrive at
the same structure where you have your
abstract operation abstract try uh
really the same implementation abstract
time again the same implementation and
then abstract operation and the same
permutation so really no difference
between the two what should you be using
in this situation you shouldn't be using
abstract classes because at that point
you can actually bolt on more
responsibilities to this operation
rather than just being used in this
mechanism if all operations are sharing
some kind of commonality between all of
them which is not present over here you
should be reaching for abstract classes
and again to reiterate in this example
we don't have that commonality so
there's no reason to use an abstract
class unless you're actually foreseeing
that commonality coming in the future
then you want to opt in for an abstract
class now for favoring interfaces there
are just some things that you you can do
with interfaces that you cannot do with
abstract classes and here we have the
first example I am naming it Scopes
because you can effectively control how
much of the object you want to access
using an interface so for example we
have states that you can initialize and
that after initialization it is ready to
be read so we accept some kind of state
we initialize it and then it's ready to
be consumed where we cannot change it we
cannot reinitialize it again effectively
giving us immutability and a way a
structured way to use our code so we
can't actually make mistakes another
things that interfaces can be used for
and it's very rare in the C world but a
concept called traits or roles where you
have some kind of context where the
functionality only belongs to that
context a class that can be used inside
that context implements this interface
effectively enabling this programming
Paradigm which you cannot do with
abstract classes because if you have
many context many roles and a class can
play many roles you should be able to
implement multiple interfaces if these
are abstract classes you can only play
one role which defeats the whole purpose
of this Paradigm so interfaces can only
be used in these scenarios and by the
way for Scopes you can get away with
using classes for it but you're going to
have to create a new class with its own
individual functionality and if you have
shared States between those classes and
you have to constantly transition it it
just becomes more code volume rather
than bolting on all of those Scopes onto
one class okay and now for the big
debate of inheritance versus composition
inheritance meaning you are trying to
use classes and Abstract classes and
inheritance in order to extend your
application or extend Behavior or add
more Behavior to your application and
then composition is for interfaces where
you're decoupling everything with
interfaces and then composing it
together it's uh not really a big debate
everybody will generally tell you prefer
composition over inheritance and I
generally agree however in this example
we are implementing the same thing in
two different ways using abstract
classes and interfaces and you're going
to see that okay
inheritance has its place with some
benefits however composition also has
its benefits and we're going to see what
they are in just a second here we have
an example we want to send an in
interface there is some kind of
commonality and abstraction between all
of the notifications that we can send
where we check should this notification
be sent and should we execute it these
are the two main abstractions we have a
check and we have an execute when we
want to alert an admin this is what the
this is the condition that we're
checking and this is the actual
execution Logic for how we're sending a
notification then we have a notify sweet
spot so again condition and then
actually sending the the notification
currently these two implementations are
the same however imagine that we're just
getting different users that we want to
notify the notification itself is a
slightly different slightly different
text subject are we sending to mobile
email right so this can vary quite a bit
but understand that what we have here is
we have a coupling between a condition
and the actual Logic for executing a
notification to this notification
abstract class into this process over
here and this yields us a very succinct
way of expressing what notifications we
have and for what reasons and to where
and how they're being sent the downsides
here is that this logic cannot be reused
in other places now if there are no
other places to use it in this is 100%
fine this is preferable if this logic
should be used in other places you go
with interfaces your de coupling
notifications from the actual way that
you're sending notification and you
decoupling it from how you're actually
going to perform the check you create
interfaces for it so you have some kind
of constraint and you have some kind of
notification that you want to perform
and then to replace that abstract class
we actually have a class where we're
composing the interfaces together and
then we're performing The same logic and
then the individual implementations
here's the admin constraint The Sweet
Spot constra straint and then the actual
notification constraint these can now be
surfaced in any other place in your
application and where you're actually
using them at those points you actually
have to compose this feature together so
the second option a lot more flexible
but also a little bit more verbose and
that is the main trade-off that you have
between interfaces and Abstract classes
and inheritance and composition
inheritance when used correctly you have
very succinct code which can only really
be present in one place and you don't
have to wonder about if it's being used
in another place these are really
isolated units where these notifications
are notifications it's not a thing that
behaves like a notification that can be
placed anywhere within your application
where with interfaces the reason people
will just say just prefer composition
because then you don't have to make this
distinction between H is this a thing
that doesn't need to be used anywhere
else you just Define your interfaces
everything is decoupled and then you
have to explicitly start defining places
where they compose and then you actually
have to do the composition or
orchestration at some point by going
default composition you're paying the
price of code volume and complexity you
have a lot more components however that
is going to give you flexibility over
implementations with inheritance you
generally get a very succinct
implementation where the logic is very
closely collocated and depends on each
other so if the structure is correct
it's very hard to mess it up up the
potential price that you need to pay
with inheritance is that abstract class
that you have extracted if that
abstraction has to be used in other
places other than these set of classes
that you extracted the common the
commonality from then you're in trouble
then you will need to go ahead and
refactor your code into it being an
interface and start defining these Place
places of composition and this will be
it for this video thank you very much
for watching hopefully you have found it
useful if you did don't forget to leave
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