Singleton Design Pattern | Implementation with details & code ✌🏻

[@arjungupta250]

Thanks a ton Keerti! Such an awesome video including the multithreading handling part which was unexpected, and while learning I enjoyed it throughly. Paused the video in between to like it because this video and this design pattern series deserves it. Looking forward for next videos in the series :D

[@KeertiPurswani]

Thank you so much. Sorry for releasing the rest of the series late but finishing it soon ❤️😇

[@vaibhavjain8672]

Thanks a lot, Keerti. I am fresher and was super scared when I first check what it is online, but you made it super simple that even a fresher who barely knows these concepts in detail can understand it. Super happy learning this in such a simple way.

[@whynesspower]

To restrict access to the operator=, you can declare it as private in the class definition, as you've already done. However, you should also provide an empty definition for it to make it inaccessible and avoid compilation errors. Here's how you can do it: cpp code private: Logger& operator=(const Logger&) = delete; Adding = delete explicitly specifies that the copy assignment operator is deleted and cannot be used. This way, any attempt to use the copy assignment operator will result in a compilation error

[@pratikwadekar4981]

Hey Keerti, This was really great explanation. Most videos would stop showing the implementation about singleton design pattern. But the fact that you showed how to make them thread safe was a cherry on top. One request though, could you increase the font size or zoom in into your code editor in upcoming videos as it becomes difficult when viewing on phone.

[@KeertiPurswani]

Thanks Pratik. Will definitely increase more from next time😇 Feedback like yours helps me improve in every video❤️😇

[@ishajindal7862]

Keerti this is by far the best video I have watched. The way you simplify everything and explain things with so much calm, simplicity is just amazing. Waiting for this entire series. It's great learning this with you. Thankyou so much :)

[@swatiacharya9073]

I use to always skip the design pattern concepts..but with your videos...its so easy to understand...i look forward to other videos... great work thanks for sharing the knowledge wirh us...😍

[@AdityaNakhare]

In a main method, you can create a singleton class instance before creating a thread. There won't be any contention issue, locking is also not needed.

[@RohitRaj-qv5nq]

Wonderful explanation Keerti, It is hard to find Oops tutorial in C++ and you have handled it easily. Thanks a lot again.

[@KeertiPurswani]

Thank you so much! Means a lot! Please do share with your friends! ❤️

[@MilindKTechnology]

Thank you ma'am. I have a question. If you null pointer check for loggerInstance on Ln. 21 then do you really think null check required on Ln.24 as well

[@mayankprabhakar5336]

Thanks for such a simple explanation!! I have one Q. Should I also delete "move constructor" & "move assignment operator" in singleton class? If YES or No, explanation would be very helpful.

[@kedarsadhu2816]

Thanks a lot Keerti. This is the most complete video I have seen so far. I like the way you explain "WHY" we need to do it. Really appreciate your work.

[@KeertiPurswani]

Thank you so much! Means a lot! Hoping you like rest of the videos as well! ❤️😇

[@AnupTiwari-n3v]

Thanks for the video Keerti. Simple and detailed. Good work!!

[@sanjaygatne1424]

बहोत अच्छेसे और गहराईसे समझाया. फाॅंट का आकार बडा होता पढने मे आसानी होती. नलपीटिआर् दो बार चेक हो गया है. जगह और वेग के संबंध मे.

[@sohelsheikh1934]

For Java People, to handle multithreading do below changes in Logger class - public static Logger getLogger() { if(logger == null) { logger = getInstance(); } return logger; } synchronized public static Logger getInstance(){ if(logger == null) return new Logger(); else return logger; }

[@PkSam07]

Awesome explanation! but I think you missed to explain why we should go for singleton pattern? I think you mentioned in order to avoid multiple logs in different places? I didn't get that?

[@SugamMaheshwari]

Lovely explanation of double checking before locking for thread-safe single ton logging🔥

[@insofcury]

Keerti awesome work on the video. I do have a suggestion though. It would be great to if you have have those multiple files in the split window so that it is easily to reference and connect while watching the video itself. This is one way to do it, but the idea is to have visibility or maybe use lesser files. I totally understand that this way it is much more modular but I think for watching everything on a single screen helps better.

[@aryanyadav3926]

Once we have checked that loggerInstance==nullptr, why is there a need to check it again, can't we just apply the lock and create a new loggerInstance as we know that it is null?

[@Aman-pd4bg]

Baat me dum hai

[@RohitKumar-sb4qc]

No, that would miss the case when both the threads have gone passed by the first if-condition, they both will eventually access the constructor, though one after the other. That's why the second if-condition is a must too

[@47hriday]

Its best explanation about singleton.Thank You.

[@VY-zt3ph]

Fantastic video. I came here after hearing your interview experience. I learned MULTITHREADING just to understand this video.

[@KeertiPurswani]

Woah! How awesome is that! ❤️😇

[@VY-zt3ph]

@@KeertiPurswani Thank you Di

[@mohanganesh1055]

Mam, please complete the design pattern playlist as fast as possible.

[@PRANAVMAPPOLI]

Hey, thanks for the awesome explanation. Why we need the 2 if check, cant we remove the inner if check?

[@akshayyadav6854]

Have the same question...

[@shankarBinnar-xl8en]

Thanks Keerti for this video..learn singlton design pattern in detailed . can I get your codes on any website ??

[@mayurbadwaik6401]

wonderfull explantion keerti, one doubt -> as explained to use mutex, can we follow this approach -> run 1st thread and after that remaining threads -> anyways we are just blocking 2 threads to make instances for the first time and after the instance is created it would not matter how many threads access it

[@roushanraj8530]

Thank you very much Di, got this from end to end like thread safe and all.... One doubt why we use .hpp and .cpp files both..... we can't do in .cpp file only, its little bit confusing to me, i haven't code like this in cpp And please add more videos.... this Playlist is going to be best on KZbin for LLD and system design 💯💯

[@osamayounus4867]

Thanks for these videos. One thing which would help with visibility is if you can show all open code files side by side

[@KeertiPurswani]

But you won’t be able to see the code clearly on screen. I am going to upload all to github pretty soon!

[@theSeniorSDE]

keerti please do a parallel code for java as well.

[@sivakumardugana3272]

Very clear explanation with examples. Thanks Kreeti

[@aloklakhotia7251]

Great video. Thanks for this. :D One doubt: Isn't the inner if condition redundant as the lock is already captured?

[@KeertiPurswani]

Thanks Suraj. For explaining so well! ❤️😇

[@geeksentertainmentmedia4827]

And "upper if" to just stop "locking" once you have created the instance.

[@shashankcool]

Thanks Keerti for such crisp & nice video capturing all the necessary points related to singleton design pattern. Really appreciate for posting such videos which helps the entire developer community.

[@KeertiPurswani]

Thank you so much, means a lot! Hoping you will like the new videos as well! 😇

[@venkatkrishna3774]

Please increase the font size when you write code or zoom in a bit. Difficult to read from distance. Thanks

[@srilakshmiuvpakala3267]

Hi Keerthi, thanks a million for the wonderful videos. I have one question in implementation of singleton design pattern. "Why do we need to make assignment operator in private. Assignment operator gets called when we try to assign existing object to another already existing object. In other words this gets called only when we have two instances already created which we already prevented from happening by making default and copy constructors private.

[@anonymoushacker9094]

Isn't it better to use static class for logger rather than singleton pattern. Some of the useful example can be parking lot

[@powprashant]

Hello Keerti, Thanks for the video, but this is still not complete. Particularly the ownership of the instance, how the instance will be released/destroyed. You can use smart pointer (since C++11) But the best would be using Meyer's Singleton that works with C++98 and C++O3 as well

[@amithtripst9851]

Could you please let us know what is the IDE you are using for practice?

[@RaisShaikh-bs7dh]

Thanks Keerti, Such a great video including each smaller things in it. One request if you can give one session on only mutex and semaphore will help us a lot. Thank you so much again for this wonderful session.

[@KeertiPurswani]

Will do for sure!

[@bheemsenkulkarni2471]

Thanks Keerthi, this was a very good explanation about singleton

[@JRKrishna-d1e]

Thanks Keerti! Very good way of explanation. God bless you.

[@sammetajhansi8063]

Thanks Keerthi! Your explanation was very excellent.But I had a doubt.Instead of using header files can't we write all the code in a single file?.Will there be any issues in doing so? Because not everyone can create those header files that easily.I am a fresher basically So I wanted to know if this is the actual convention to be followed or if it is also fine to code everything in a single file.

[@krishnasummer5603]

Hi sis, your explanation is very clean & good, if u can add more design patterns .It'll be a great help. Thanks.

[@arkosnatoneogy2366]

after you implement the double checked lock is the inner if condition needed any more? isnt it bound to be TRUE?

[@vipulpurbey4323]

goldmine of a video

[@whynesspower]

20:05 can you give me the code for that? Will it be something like delete Logger operator=(const Logger &)? Correct me if I am wrong

[@sasageyo9571]

Are freshers (university grads ) expected to face these questions ? Great video btw !!!

[@durgeshrai04]

Thanks a lot Kreerti! for the wonderful explantion of singleton design pattern.

[@KeertiPurswani]

Thank you! Hope you like other videos on the channel as well! 😇

[@SourabhDesaiBrief]

Clearly Visible, Thank You :) It complied on first time, on staging code - Truly magical!

[@KeertiPurswani]

Thank you! A lot of effort goes behind every single video! ❤️

[@Ww-ul8oe]

Thank you Keerti. Appreciate implementing in c++

[@KeertiPurswani]

Thank you! Please do subscribe and share the video with your friends❤️😇

[@virendramane7818]

Thank you Keerti! Really appreciate your work.

[@nileshpatil4111]

Nicely explained. Understood it completely

[@kingshahzadaamir]

Hey Keerti, I tried this on gcc linux terminal. without mutex also it gave single instance all the time. spent 15 minutes to figure out what wrong I wrote. but then tried it on online gdb compiler; there it varied then.

[@vivekshivhare8820]

Can we delete the second time nullptr checking as we are already checking it for mtx locking, or that can also cause some problem? just curious, please do reply..

[@AshishIkhar-k7b]

Thanks Keerti, can you please record the session on "Smart Pointer"

[@svarajdhanulkar1791]

Yar jo wo problem tha like k if Multithreading is in picture then singleton fails or tabhi muje realise hua uska bhi jugad hota hai par ye interview me pucha tha or sch me tabhi realise hua k hmm such a diff pov

[@nehakale9427]

Excellent explaination Keerti!

[@amarnathsama]

Can someone explain why we need to have objects of the class at all? why can't getLogger function be static also?

[@Kaushikraj9845]

Assuming if we write the code in java ..Can we create object during initialization like below public class Singleton { private static Singleton singleton=new Singleton();; private Singleton() { super(); } public static Singleton getSingleton() { return singleton; } }

[@guruprasad_sannenahalli]

Thanks Keerti. Very useful.

[@mayankrai7938]

Finally back ☺️

[@KeertiPurswani]

With many many videos this time❤️😇

[@paraskaushik2639]

Why have you made 3 files ? logger.hpp , logger.cpp and user.cpp . why cant we directly used logger.hpp in user.cpp ? is there some pattern , folder structuring you have followed ?

[@meme_engineering4521]

excellent!!, can someone please tell me if this playlist is enough for sde1 interviews?

[@tarunkumar7656]

AWESOME, Great work!

[@AnkitaSingh-vv5rc]

Thankyou so much, Keerti Mam

[@athena2986]

Thank you for explaining in detail.can you please create GitHub links for the codes specially the design pattern ones

[@ritikapande21]

Hey Keerti, Really a good video and detailed explanation. Hats off and please continue to contribute.

[@KeertiPurswani]

Thank you so much Ritika, means a lot! More videos coming up soon ❤️😇

[@kartheekgoud9009]

Thanks Keerthi.. Really great explanation 👏.

[@rosansenapati-pl5hr]

wonderful explanation thank you so much for teaching us

[@KeertiPurswani]

Thank you! Please do share the video with your friends!

[@rosansenapati-pl5hr]

@@KeertiPurswani ofcourse I will this is great stuffs and people need to know about your amazing videos

[@siddeo85]

nice video but could you make videos using java?

[@shyamchauhan520]

Nice explanation :) One doubt: when are we going to delete the resource(loggerInstance) which we have created dynamically using new keyword.

[@rohitsankarpal7866]

Can someone help me with VS Code as the thread is not supporting !! Any idea how to resolve that ?

[@rahulsagarvoduru5158]

You are a great teacher !! Thank You !!

[@mrCetus]

One Request: Please give the direct link to the playlist of design patterns you are covering to check other patterns easily.

[@KeertiPurswani]

There’s a playlist on the channel - Design Patterns kzbin.info/aero/PLliXPok7ZonlZJuAN0hvUnf5ovFepjxU0 😇😇

[@aryankumar87771]

wait wait what was that at the last? making constructor private and operator overloading private... as a non C++ coder that hit me like a train

[@j.r.krishna1122]

You made my day

[@AnkitSingh-lb9fj]

great stuff as always, waiting for next video on design pattern

[@2008suryan]

Very good clear explanation. Expecting more videos on other design patterns.

[@057anmolkesarwani4]

such good explanation

[@niksgupta36]

In Double-checked Locking, instead of adding another nullpointer check, could we have just added mtx.lock() and unlock() inside the initial nullpointercheck? Should work right. Let me know.

[@geeksentertainmentmedia4827]

You mean putting lock inside if? It would have same problem . Two threads would have entered inside the "if " condition , and then lock would have happened. So one thread would create instance , unlock , then another would have created instance.

[@niksgupta36]

@@geeksentertainmentmedia4827 Makes sense now. Thanks.

[@bsratuoh]

It is really a great session and helpful. Thanks for this. If possible pls increase the font size while explaining codes.

[@KeertiPurswani]

Thanks for the feedback! Hoping it’s better in the present videos! ❤️😇

[@RishabhRD]

If you are writing singleton in C++... Meyers singleton is the standard way of doing this. I guess covering meyers singleton was super important not done.... BTW singletons are anti pattern avoid it

[@Archak77]

Excellent video ...simple explaination 👍

[@KeertiPurswani]

Thank you so much! Please do share with your friends?

[@potassium_cyanide_boy8515]

What if exception is thrown Inside a mutex lock ? It will never ever unlock the mutex and no other thread will be able to enter the critical section or they will keep waiting to mutex to get unlocked that will never happened. So we should use unique_lock or lock_guard i guess 😒😒

[@simpleguy2020]

Does it not make unit testing the code hard

[@matheens6689]

You can use semaphore ? Why mutex

[@rohit_kapdi]

Superb explanation. ❤

[@KeertiPurswani]

Thank you! Hope you like other videos as well! 😇

[@Luckygangff]

When we delete the instance and created new instance 2nd time in main we are unable to delete the instance which we created 2nd time getting double free error

[@kushagrabhardwaj4436]

Thank you so much for this series :)

[@hrudayd4217]

Normally front end developer uses js, learning dsa using js is it useful or not ?

[@KeertiPurswani]

Dsa is useful for sure (language doesn’t matter that much - as long as you can solve questions) But I do know some front end developers who are doing really well and don’t know dsa much.

[@sheshitkarthikeya1528]

Your effort to keep things simple is amazing...Also don't worry no one will steal your logger constructor.😂

[@KeertiPurswani]

Hehe thank you so much! ❤️❤️

[@PROTECHRAHUL]

Hey diii i didn't get what are you teaching can you please tell? So i can learn it.

[@KeertiPurswani]

Hi Rahul, start watching the design pattern playlist. The first video is introduction of what design patterns are. It should help. Let me know if you have any doubts😇

[@PROTECHRAHUL]

@@KeertiPurswani Thanks dii. 🤗

[@jenishadsouza907]

Really great explanation!!!

[@integrateeverything]

Hi didi ,your videos are just awesome keep making videos like this and motivating us

[@KeertiPurswani]

Thank you! Please keep sharing videos and motivating me! ❤️

[@ArchanaBiradar-l5h]

How about KZbin adding search option in comments section.

[@skandan6266]

Please make the code view bigger. It becomes difficult to read while watching on a phone

[@nkjat123]

Hi Guys.. awesome videos

[@vishalsethi4024]

Great Teacher YOU are

[@KeertiPurswani]

Thank you! Means a lot❤️😇

[@vinamrajha1571]

You forgot to return as reference when you overloaded the assignment operator.

[@fakecake7608]

Great complete Video :)

[@nikhillaad941]

awsome explaination

[@tech_wizard9315]

Please provide best resume templates for freshers to apply for tech giant's. It's need of many students

[@KeertiPurswani]

Will do!

[@mobin1457]

Perfect work