Composition over Inheritance

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This is a weekly show where we try to become more confident and excited about programming by learning intriguing things that we didn’t know before. Today, we are are going to talk about composition over inheritance. Inheritance is when you design your types after what they are, while composition is when you design your types after what they cando. We are going to learn about the limitations of inheritance, and how to solve them using composition.

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[thiagotimm]

"The problem with inheritance is that encourages you to go predict the future..." Just genius Matt!

[AlexandriaRohn]

07:03 "Inheritance encourages you to build this taxonomy of objects very early on in the project. And you are most likely going to make big design mistakes while doing that. Because humans cannot predict the future."

"I think it's just better to use composition from the start. It's more flexible, it's more powerful, and it's really easy to do."

[Aleh_Loup]

Composition gets better with Object Spread (sugar for Object.assign):

return {...barker(state), ...driver(state), ...killer(state)}

[ThomasBurleson]

Inheritance is appropriate for single-level abstract classes where you define expectations of abstract methods that MUST be defined in a subclass. You effectively have written a API-contract. In almost all other cases, I favor composition. I love your videos and the style of teaching [often] techno-jargon.

[ahmarsiddiqui]

07:03 turning point of my perception of programming in general

I always found it hard to implement inheritance in real world applications but still used it thinking that's how I was taught oop and that's how I'm suppose to write programs

thanks a lot for such a great video

[SlhT-xecc]

I really love how extremely simple your example are presented! it really makes me roll my eyes when "beginner" guides use long-winded examples where you have to think about a thousand things at the same time and get confused and lost in concepts unrelated to what you're actually trying to learn.

[BenRangel]

I blame the overuse of inheritance on college focusing too much on OOP and training us to overuse that pattern, and cram inheritance into our projects.
A perfect inheritance hierarchy is a wonderful thing that gives you a sense of structure and a mental model. But it's not feasible in today's agile world cause it's unmaintanable. Most agile projects would benefit from using composition.

[Avatan]

Here from The Odin Project. Great video, very helpful, and explained in a fun way too! Thank you!

[praguepanda]

This is a nice explanation. What you consider "composition" is however called "concatenative inheritance". Composition is achieved by passing more specialized components into a more general one. By doing so, you create an object model tree in which objects reference and use other objects rather than making a type tree (taxanomy) in which objects are tightly coupled to their parents (prototypal delegates or parent classes) as opposed to loose coupling in case of composition.

[thinkcritically]

For those browsers that don't support Object.assign yet:

if( !Object.assign ) {
Object.assign = function( obj, items ) {
var src = Object( items), target = Object( obj )
Object.getOwnPropertyNames( src ).forEach( function( k ) {
target[ k ] = src[ k ]
})
return target;
}
}

[anthonychung]

I'd LOVE it if you gave sample "tasks" for us to do to test ourselves. it sounds suspiciously like homework but it's the only way I could ever confirm I understood anything. haha

[Rashomon]

MPJME - I've been a developer for almost 20 years. I've developed in multiple languages - COBOL, ActionScript, Objective C, Java, JavaScript, PHP, etc. I feel like I've always been "behind the curve", because I've had to learn so many languages (frequently starting over). I just discovered your channel last week, and I've been binge watching, because I have learned a LOT from them. You are filling in the pieces that I've been missing from being a "self-taught" developer. I feel like I'm now becoming the top-notch developer that I've always wanted to be. THANK YOU!!!

[youAmera]

Program to an interface and not an implementation - this is a good practice

[bobbyadamson]

I have spent about a week reading things that dance around what you have explained so clearly here. Thank you for all you do

[robroem]

I just have to say: You give the best example of WHY composition should be favored that I've ever seen. Anytime someone asks me, or this topic comes up; I immediately link them to your video. You explain so much better than I ever could. Thanks for that!

[peripona]

At First.. I felt reluctant to watch the video with such Handsome Poster Image ( : Scarcastic :D )
But then...
I am spellbound by the way you have conveyed such a concept with such innovative, indulging and entertaining way..
Kudos. Yo!! your video rocks. I ill subscribe and follow your Videos :)

With love from India !

[darrenandveronica]

I had a dream about trying to flesh out a new program with inheritance. I woke up sweating. That's totally true. Man this video was great. I watched quite a few of your vids now, you crack me up.

[MopeyFand]

The amount of time saved by my brain trying to figure out how to adapt classes for abstraction.
I've just switched back to more of a functional paradigm from OOP, and it's quite refreshing.
Composition for the win.

[tarekghosn]

hell the first few lines were enough to put it in place. i found you after15 plus videos and yours was the only one who truly explained the difference in how to use them directly while thinking
sanks

[FairyRat]

This is so cool! I'm totally on board with composition. Also HUGE thanks for your work! Awesome stuff! The Odin Project represent!