As a developer, sometimes you hammer away on some useless solo side project for a few weeks. Maybe a small game, a web interface for your home-built storage server, or an app to turn your living room lights on an off.

I often see these posts and graphs here about motivation, about a desire to conceive perfection. You want to create a self-hosted Spotify clone "but better", or you set out to make the best todo app for iOS ever written.

These rants and memes often highlight how you start with this incredible drive, how your code is perfectly clean when you begin. Then it all oscillates between states of panic and surprise, sweat, tears and euphoria, an end in a disillusioned stare at the tangled mess you created, to gather dust forever in some private repository.

Writing a physics engine from scratch was harder than you expected. You needed a lot of ugly code to get your admin panel working in Safari. Some other shiny idea came along, and you decided to bite, even though you feel a burning guilt about the ever growing pile of unfinished failures.

All I want to say is:

No time was lost.

This is how senior developers are born. You strengthen your brain, the calluses on your mind provide you with perseverance to solve problems. Even if (no, *especially* if) you gave up on your project.

Eventually, giving up is good, it's a sign of wisdom an flexibility to focus on the broader domain again.

One of the things I love about failures is how varied they tend to be, how they force you to start seeing overarching patterns.

You don't notice the things you take back from your failures, they slip back sticking to you, undetected.

You get intuitions for strengths and weaknesses in patterns. Whenever you're matching two sparse ordered indexed lists, there's this corner of your brain lighting up on how to do it efficiently. You realize it's not the ORMs which suck, it's the fundamental object-relational impedance mismatch existing in all languages which causes problems, and you feel your fingers tingling whenever you encounter its effects in the future, ready to dive in ever so slightly deeper.

You notice you can suddenly solve completely abstract data problems using the pathfinding logic from your failed game. You realize you can use vector calculations from your physics engine to compare similarities in psychological behavior. You never understood trigonometry in high school, but while building a a deficient robotic Arduino abomination it suddenly started making sense.

You're building intuitions, continuously. These intuitions are grooves which become deeper each time you encounter fundamental patterns. The more variation in environments and topics you expose yourself to, the more permanent these associations become.

Failure is inconsequential, failure even deserves respect, failure builds intuition about patterns. Every single epiphany about similarity in patterns is an incredible victory.

Please, for the love of code...

Start and fail as many projects as you can.

Good Morning!, its time for practiseSafeHex's most incompetent co-worker!

Todays contestant is a very special one.

*sitcom audience: WHY?*

Glad you asked, you see if you were to look at his linkedin profile, you would see a job title unlike any you've seen before.

*sitcom audience oooooooohhhhhh*

were not talking software developer, engineer, tech lead, designer, CTO, CEO or anything like that, No No our new entrant "G" surpasses all of those with the title ..... "Software extraordinaire".

*sitcom audience laughs hysterically*

I KNOW!, wtf does that even mean! as a previous dev-ranter pointed out does this mean he IS quality code? I'd say he's more like a trash can ... where his code belongs

*ba dum tsssss*

Ok ok, lets get on with the show, heres some reasons why "G" is on the show:

One of G's tasks was to build an analytics gathering library for iOS, similar to google analytics where you track pages and events (we couldn't use google's). G was SO good at this job he implemented 2 features we didn't even ask for:

- If the library was unable to load its config file (for any reason) it would throw an uncatchable system integrity error, crashing the app.
- If anything was passed into any of the functions that wasn't expected (null, empty array etc.) it would crash the app as it was "more efficient" to not do any sanity checks inside the library.

This caused a lot of issues as some of the data needed to come from the clients server. The day we launched the app, within the first 3 hours we had over 40k crash logs and a VERY angry client.

Now, what makes this story important is not the bugs themselves, come on how many times have we all done something stupid? No the issue here was G defended all of this as the right thing to do!

.. and no he wasn't stoned or drunk!

G claimed if he couldn't get the right settings / params he wouldn't be able to track the event and then our CEO wouldn't have our usage data. To which I replied:

"So your solution was to not give the client an app instead? ... which also doesn't give the CEO his data".

He got very angry and asked me "what would you do then?". I offered a solution something like why not have a default tag for "error" or "unknown" where if theres an issue, we send up whatever we have, plus the file name and store it somewhere else. I was told I was being ridiculous as it wasn't built to track anything like that and that would never work ... his solution? ... pull the library out of the app and forget it.

... once again giving everyone no data.

G later moved onto another cross-platform style project. Backend team were particularly unhappy as they got no spec of what needed to be done. All they knew was it was a single endpoint dealing with very complex model. There was no Java classes, super classes, abstract classes or even interfaces, just this huge chunk of mocked data. So myself and the lead sat down with him, and asked where the interfaces for the backend where, or designs / architecture for them etc.

His response, to this day frightens me ... not makes me angry, not bewilders me ... scares the living shit out of me that people like this exist in the world and have successful careers.

G: "hhhmmm, I know how to build an interface, but i've never understood them ... Like lets say I have an interface, what now? how does that help me in any way? I can't physically use it, does it not just use up time building it for no reason?"

us: "... ... how are the backend team suppose to understand the model, its types, integrate it into the other systems?"

G: "Can I not just tell them and they can write it down?"

**
I'll just pause here for a moment, as you'll likely need to read that again out of sheer disbelief
**

I've never seen someone die inside the way the lead did. He started a syllable and his face just dropped, eyes glazed over and he instantly lost all the will to live. He replied:

" wel ............... it doesn't matter ... its not important ... I have to go, good luck with the project"

*killed the screen share and left the room*

now I know you are all dying in suspense to know what happened to that project, I can drop the shocking bombshell that it was in fact cancelled. Thankfully only ~350 man hours were spent on it

... yep, not a typo.

G's crowning achievement however will go down in history. VERY long story short, backend got deployed to the server and EVERYTHING broke. Lead investigated, found mistakes and config issues on every second line, load balancer wasn't even starting up. When asked had this been tested before it was deployed:

G: "Yeah I tested it on my machine, it worked fine"

lead: "... and on the server?"

G: "no, my machine will do the same thing"

lead: "do you have a load balancer and multiple VM's?"

G: "no, but Java is Java"

... and with that its time to end todays episode. Will G be our most incompetent? ... maybe.

Tune in later for more practiceSafeHex's most incompetent co-worker!!!

I have a bunch of contesters fort the worst interview.

#1 The Dishonest Ignorant

Me: *asks question*
#1: *stumbles*
Me: It's okay to say that you don't know.
#1: *continues to ramble on without making sense*
Me: Well, okay. That is all. I don't think that this will be a fit.

#2 The fraud

Me: How would you rate your knowledge in object orientated programming?
#2: Very advanced! I am an expert!
Me: Can you state the difference of an interface and an abstract class?
#2: *surprised pikachu-face* Well not that advanced!

#3 The trickster

During a skype call (without video):

Me: *asks question*
#3: *keyboard sounds aclacking*
Me: Are you googling?
#3: No *click clack click a clack* ... and to answer your question: *starts reading from the first search results*

The real bummer is, that in all of these cases, just saying "I don't know" would have been fine. (The "expert" OOP-guy would still have some explaining to do.)

It's not like that our interview process resolves around trick questions or that you'd get kicked out for getting one answer wrong. Though how can I trust somebody not to lie to me on a daily basis if they fake their interview?

We keep the interview relatively basic and rely on real-word coding exercise anyway and it helps us to get an idea on where we would gain support from them and where we need to support them.

As a developer you spend a lot of time learning new stuff anyways.

It blows my mind.

You want to land a job as PHP developer? About to go to an interview?

There are two ways:

1. Be able to explain the difference between an interface and an abstract class and their purposes. (I shit you not.)

2. If you aren't able to, then simply state you don't know and are eager to learn.

(The second approach might not work if you claimed to know object oriented programming "very well" before though.)

Yet I am astounded in how many interviews people were either playing smart and just rambled on not wanting to lose face. During the remote calls of some special candidates I could even hear them typing on their keyboards in the background googling the answers to my questions.

And the irony is that I thereby had to veto their appliance. As they had lost my trust in being able to communicate honestly. And for wasting my time.

Our domain is complicated and ever-changing and not knowing certain parts of software development is *normal*.

Yet don't just try to fake it in order to land a job. It won't work, and when it does you may find yourself literally in the company of like-minded individuals.

Ok, so when I inherit a Wordpress site I've really stopped expecting anything sane. Examples: evidence that the Wordpress "developer" (that term is used in the loosest sense possible) has thought about his/her code or even evidence that they're not complete idiots who wish to make my life hell going forwards.

Have a look at the screen shot below - this is from the theme footer, so loaded on every page. The screenshot only shows a small part of the file. IT LITERALLY HAS 3696 lines.

Firstly, lets excuse the frankly eye watering if statement to check for the post ID. That made me face palm myself immediately.

The insanity comes for the thousands of lines of JQuery code, duplicated to hell and back that changes the color of various dividers - that are scattered throughout the site.

To make things thousands of times worse, they are ALL HANDED CODED.

Even if JavaScript was the only way I could format these particular elements I certainly wouldn't duplicate the same code for every element. After copy and pasting that JQuery a couple of times and normal developer would think one word, pretty quickly - repetition.

When a good developer notes repetition ways to abstract crap away is the first thought that comes to mind.

Hell, when I was first learning to code god knows how long ago I always used functions to avoid repetition.

In this case, with a few seconds though this "developer" could have created a single JQuery handler and use data attributes within the HTML. Hell, as bad as that is, it's better than the monstrosity I'm looking at now.

I'm aware Wordpress is associated with bad developers due to it's low barrier to entry, but this site is something else.

The scary thing is that I know the agency that produced this. They are very large, use Wordpress exclusively and have some stupidly huge clients that would be know nationally.

Wordpress truly does attract some of the most awful "developers" and deserves it's reputation.

If you're a good developer and use Wordpress I feel sorry for you, as you're in small numbers from my experience.

Rant over, have vented a bit and feel better. Thanks Devrant.

How come it is so hard to find good developers. Have been doing interviews for a couple of weeks now (for a senior PHP developer role).

First round is me talking about the function and company, asking questions about candidates experience, wishes and we usually end in some tech conversations. Most of the resumes I got are pretty fucking good. I mean, experience with low-level languages, experience with the problems we need to solve here, contributions to open-source, experience in R and MathLab etc etc. On paper they look perfect.

For the second round I give them an assessment which they can do at home on their own machine in their own time. It's not a hard one, just some mathmatical problems they need to solve. A quick google GIVES the answer (no joke!!). But that's OK, I look at their code cleanliness, proper use of commenting so I can determine if they are solo-developers or fit good in a team and if they abstract repeated functions and make sure that they take their work seriously, you know the drill.

It pisses me off that I get BROKEN FUCKING CODE WHICH DOES NOT EVEN RUN and that I get code back which I look at and makes me vomit instantly, I mean, DO YOU EVEN TAKE YOUR PROFESSION SERIOUS? How dare you to ask for 50k the year, a lease-car, extra bonusses AND YOUR FUCKING CODE SPITS OUT COMPLETLY WRONG ANSWERS OR DOES NOT EVEN RUN WHAT THE FUCK DUDE GO BACK TO FROM WHICH EVER HOLE YOU CRAWLED OUT AND STOP WASTING OTHER PEOPLES TIME WITH YOUR FUCKING INCOMPENTENCE...

7 page resume
13 jobs, some only lasting 3 months
TONS of grammatical and spelling errors.
Descriptions of each job has several lines just saying he "created functions; interfaces; abstract classes; classes".... For a jr/senior level developer job? Why are we interviewing him?

For a .net developer is it normal not to know what an abstract class is? I interviewed someone today that didn't know, and a colleague told me it wasn't that unusual.

To me this is the same level as knowing what an interface is

Bad managers, rude clients and annoying colleagues...

A lot of the stories here I read have at least any of the words listed above. My advice to most of you guys is: LEAVE.

And do it NOW.

The thing is, most of the stuff you're complaining about won't change. And you will be stuck there longer than you want to be and/or notice, trust me i've been there.

Especially the rude client part is where I've had lots of experience in, you have to search for a company which will abstract that layer for you. If you're on here most likely you're a developer and not everybody is a team lead. So why the F in hell are you even in conversations about budget and/or are you doing the most of the talking in the retrospective? If your project manager is ANY good he is doing that all for you.
There is so much to choose from (my experience in western countries) so please dont be stuck in a dead end job. Or start freelancing or whatever..

When I was in college OOP was emerging. A lot of the professors were against teaching it as the core. Some younger professors were adamant about it, and also Java fanatics. So after the bell rang, they'd sometimes teach people that wanted to learn it. I stayed after and the professor said that object oriented programming treated things like reality.

My first thought to this was hold up, modeling reality is hard and complicated, why would you want to add that to your programming that's utter madness.

Then he started with a ball example and how some balls in reality are blue, and they can have a bounce action we can express with a method.

My first thought was that this seems a very niche example. It has very little to do with any problems I have yet solved and I felt thinking about it this way would complicate my programs rather than make them simpler.

I looked around the at remnants of my classmates and saw several sitting forward, their eyes lit up and I felt like I was in a cult meeting where the head is trying to make everyone enamored of their personality. Except he wasn't selling himself, he was selling an idea.

I patiently waited it out, wanting there to be something of value in the after the bell lesson. Something I could use to better my own programming ability. It never came.

This same professor would tell us all to read and buy gang of four it would change our lives. It was an expensive hard cover book with a ribbon attached for a bookmark. It was made to look important. I didn't have much money in college but I gave it a shot I bought the book. I remember wrinkling my nose often, reading at it. Feeling like I was still being sold something. But where was the proof. It was all an argument from authority and I didn't think the argument was very good.

I left college thinking the whole thing was silly and would surely go away with time. And then it grew, and grew. It started to be impossible to avoid it. So I'd just use it when I had to and that became more and more often.

I began to doubt myself. Perhaps I was wrong, surely all these people using and loving this paradigm could not be wrong. I took on a 3 year project to dive deep into OOP later in my career. I was already intimately aware of OOP having to have done so much of it. But I caught up on all the latest ideas and practiced them for a the first year. I thought if OOP is so good I should be able to be more productive in years 2 and 3.

It was the most miserable I had ever been as a programmer. Everything took forever to do. There was boilerplate code everywhere. You didn't so much solve problems as stuff abstract ideas that had nothing to do with the problem everywhere and THEN code the actual part of the code that does a task. Even though I was working with an interpreted language they had added a need to compile, for dependency injection. What's next taking the benefit of dynamic typing and forcing typing into it? Oh I see they managed to do that too. At this point why not just use C or C++. It's going to do everything you wanted if you add compiling and typing and do it way faster at run time.

I talked to the client extensively about everything. We both agreed the project was untenable. We moved everything over another 3 years. His business is doing better than ever before now by several metrics. And I can be productive again. My self doubt was over. OOP is a complicated mess that drags down the software industry, little better than snake oil and full of empty promises. Unfortunately it is all some people know.

Now there is a functional movement, a data oriented movement, and things are looking a little brighter. However, no one seems to care for procedural. Functional and procedural are not that different. Functional just tries to put more constraints on the developer. Data oriented is also a lot more sensible, and again pretty close to procedural a lot of the time. It's just odd to me this need to separate from procedural at all. Procedural was very honest. If you're a bad programmer you make bad code. If you're a good programmer you make good code. It seems a lot of this was meant to enforce bad programmers to make good code. I'll tell you what I think though. I think that has never worked. It's just hidden it away in some abstraction and made identifying it harder. Much like the code methodologies themselves do to the code.

Now I'm left with a choice, keep my own business going to work on what I love, shift gears and do what I hate for more money, or pivot careers entirely. I decided after all this to go into data science because what you all are doing to the software industry sickens me. And that's my story. It's one that makes a lot of people defensive or even passive aggressive, to those people I say, try more things. At least then you can be less defensive about your opinion.

Worst architecture I've seen?

The worst (working here) follow the academic pattern of trying to be perfect when the only measure of 'perfect' should be the user saying "Thank you" or one that no one knows about (the 'it just works' architectural pattern).

A senior developer with a masters degree in software engineering developed a class/object architecture for representing an Invoice in our system. Took almost 3 months to come up with ..

- Contained over 50 interfaces (IInvoice, IOrder, IProduct, etc. mostly just data bags)
- Abstract classes that implemented the interfaces
- Concrete classes that injected behavior via the abstract classes (constructors, Copy methods, converter functions, etc)
- Various data access (SQL server/WCF services) factories

During code reviews I kept saying this design was too complex and too brittle for the changes everyone knew were coming. The web team that would ultimately be using the framework had, at best, vague requirements. Because he had a masters degree, he knew best.

He was proud of nearly perfect academic design (almost 100% test code coverage, very nice class diagrams, lines and boxes, auto-generated documentation, etc), until the DBAs changed table relationships (1:1 turned into 1:M and M:M), field names, etc, and users changed business requirements (ex. concept of an invoice fee changed the total amount due calculation, which broke nearly everything).

That change caused a ripple affect that resulted in a major delay in the web site feature release.

By the time the developer fixed all the issues, the web team wrote their framework and hit the database directly (Dapper+simple DTOs) and his library was never used.

What do you think about my language choice set for the future (knowing I want to work as a software and app developer) ? Anything to add / remove ?

- C++: Fast and well-documented, so I think it's a standard even in the next decades to come

- Java: Although I think that this language will more likely die in the next decade, I'll maybe keep this language because some dinosaurs enterprises still rely on it. Ah and mainly because it's still widely used in Android apps programming. For now.

Talking about Android, does learning Kotlin worth it ?

- Python: Will mainly use it for automation and prototyping, but nothing more, as it seems not to be widely use in the software development field (or it is ?). I'll also keep it for hobbies, however.

- Rust: This language seems to be a rising star in the industry since it is very clean, classic, as fast as C / C++ while introducing more safety. However I'll wait a bit for this one since it requires more complicated and abstract knowledge I do not have yet.

- Javascript (or more particularly JSX): Hurts to say I'll keep it, even more than Java. I'd let it in the web development hell I won't step in if it was not used in webapps / cross-platform mobile applications. And since this kind of stuff looks trendy, I don't think I can avoid it. Plus, I liked working with React Native. Sorry.

- C#: Seems to be a must when working on Windows software interfaces, so guess I'll have to learn this one. Will do so gladly, it looks better than Java

This started as an update to my cover story for my Linked In profile, but as I got into a groove writing it, it turned into something more, but I’m not really sure what exactly. It maybe gets a little preachy towards the end so I’m not sure if I want to use it on LI but I figure it might be appreciated here:

In my IT career of nearly 20 years, I have worked on a very wide range of projects. I have worked on everything from mobile apps (both Adroid and iOS) to eCommerce to document management to CMS. I have such a broad technical background that if I am unfamiliar with any technology, there is a very good chance I can pick it up and run with it in a very short timespan.

If you think of the value that team members add to the team as a whole in mathematical terms, you have adders and you have subtractors. I am neither. I am a multiplier. I enjoy coaching, leading and architecture, but I don’t ever want to get out of the code entirely.

For the last 9 years, I have functioned as a technical team lead on a variety of highly successful and highly productive teams. As far as team leads go, I tend to be a bit more hands on. Generally, I manage to actively develop code about 25% of the time to keep my skills sharp and have a clear understanding of my team’s codebase.

Beyond that I also like to review as much of the code coming into the codebase as practical. I do this for 3 reasons. I do this because as a team lead, I am ultimately the one responsible for the quality and stability of the codebase. This also allows me to keep a finger on the pulse of the team, so that I have a better idea of who is struggling and who is outperforming. Finally, I recognize that my way may not necessarily be the best way to do something and I am perfectly willing to admit the same. I have learned just as much if not more by reviewing the work of others than having someone else review my own.

It has been said that if you find a job you love, you’ll never work a day in your life. This describes my relationship with software development perfectly. I have known that I would be writing software in some capacity for a living since I wrote my first “hello world” program in BASIC in the third grade.

I don’t like the term programmer because it has a sense of impersonality to it. I tolerate the title Software Developer, because it’s the industry standard. Personally, I prefer Software Craftsman to any other current vernacular for those that sling code for a living.

All too often is our work compiled into binary form, both literally and figuratively. Our users take for granted the fact that an app “just works”, without thinking about the proper use of layers of abstraction and separation of concerns, Gang of Four design patterns or why an abstract class was used instead of an interface. Take a look at any mediocre app’s review distribution in the App Store. You will inevitably see an inverse bell curve. Lot’s of 4’s and 5’s and lots of (but hopefully not as many) 1’s and not much in the middle. This leads one to believe that even given the subjective nature of a 5 star scale, users still look at things in terms of either “this app works for me” or “this one doesn’t”. It’s all still 1’s and 0’s.

Even as a contributor to many open source projects myself, I’ll be the first to admit that have never sat down and cracked open the Spring Framework to truly appreciate the work that has been poured into it. Yet, when I’m in backend mode, I’m working with Spring nearly every single day.

The moniker Software Craftsman helps to convey the fact that I put my heart and soul into every line of code that I or a member of my team write. An API contract isn’t just well designed or not. Some are better designed than others. Some are better documented than others. Despite the fact that the end result of our work is literally just a bunch of 1’s and 0’s, computer science is not an exact science at all. Anyone who has ever taken 200 lines of Java code and reduced it to less than 50 lines of reactive Kotlin, anyone who has ever hit that Utopia of 100% unit test coverage in a class, or anyone who can actually read that 2-line Perl implementation of the RSA algorithm understands this simple truth. Software development is an art form. I am a Software Craftsman.

#wk171

I feel like IE is an example of a deep rooted demon beast that spawns fucktarded bloat transpilers like BABEL.
When companies try to invent their own wheels, or do their own thing is when the pits of developer hell start to spawn such fucking convoluted fucktarded bullshit.

Abstract to Design:
I'm trying to think of a world where things are standardized, as boring as it sounds... Imagine if companies weren't so fucktarded with greedy smoke and mirrors, and they all contributed to making a single product standardized and workable, and improve on that product... Like a physics "Standard model" but for each product invented.

But no... here we are... 20 million ways to accomplish one similar task, with 20 million different designs, with majority adhering to their own flaws... or planned obsolecence... 10 million booby traps of consumer remorse.

Why do we do this as a society just to make some bastard company's profit margin go up, so they can keep competing in the "free market" of fuck all fuckery?

I get it.. yea... innovation... sure..
but sometimes innovation is just a means to and end of sanity, especially when they are proprietary, and especially when that proprietary shit turns to, well... shit!

In a perfect world, things will be designed open-sourced, compatible, and improved upon without "breaking" changes... but this is virtually impossible without standardization of the VERY fundamental components. But then those components can be improved, and might be smaller/lighter/more efficient by design, and simply wont work with the old versions without drastic "TRANSPILATION"

I suppose this is the way it is always going to be... Neverending stream of design "improvements". I suppose being a developer in todays world is a bittersweet existence... unless you're just trying to make ends meet... in that case. I think I might be in hell.

Take a look at web-dev today with all the "improvements" ... it's literally turned into a jungle of FUCK MY LIFE. A giant dick waiving contest with all these dicks colliding against each other in cluster fuck bombardment.

God help us all.... and now back to coding.

Am I in developer hell already? A shitty project is about to come to an end (hopefully), or should I rather say: It needs to come to an end. But I am still quite lost in how to deal with it, hence procrastinating on it - making the deadline come closer and with it the realization that I'll probably have to rewrite almost everything. I'm not sure how, but I do know that the current code is a dumpster fire.

Basically what I need to do is dealing with the APIs of different payment providers/gateways (like PayPal, AmazonPay). For most cases I'll get a payment ID from the shop and need to act on it later, e.g. capture the authorized money in the case of a credit card transaction or do refunds (without user interaction, unless there is an error). Now at first I put something together where I try to abstract the payment information into two tables:
orders{1}<->{0..n}payments
payments{1}<->{1..n}paymentDetails

Unfortunately trying to abstract the different payment methods and to squeeze them (and their different possible stati and functions) in these tables was not very successful, it's a total mess with magic numbers, half-broken behavior and without any consideration for partial payments/captures or unfinished requests (i.e. if there is an exception before the response is dealt with, there is no indication that anything has ever been sent). Also the current amount is calculated through the history of the paymentDetails table, which basically works differently for each payment type.

How to fix this mess in a way that I'll still have a job by next week?

I'm trying to improve the db schema first, as I think my biggest problems are lying there. Through some research I've come across a recommendation for making payment type specific subtables (with a magic number/string in the main table to prevent having to look up all subtables). That way I can record what I send and receive without having to abstract it too much, so I'll have an acceptable transaction log. The paymentDetails table can be removed (necessary fields go to the payments table). The payments table gets multiple fields for the amount (differentiating between open, authorized, captured, processing and refunded values) and always reflects the current status.

Tables:
payments
paymentRequestsPaypal
paymentRequestsAmazonpay
paymentRequestsXyz

I think I'm going in the right direction here. hm. Maybe there's some light at the end of this long, dark tunnel. Or a train. I'll have two days to find out.

How would you - as an experienced OOP developer - describe the difference between an abstract class & an interface to a beginner, learning the concepts?