Observer Design Pattern

Get the Code: goo.gl/EYGnQ
Best Design Patterns Book : goo.gl/W0wyie
MY UDEMY COURSES ARE 87.5% OFF TIL July 16th ($9.99)
www.udemy.com/
➡️ Python Data Science Series for $9.99 : Highest Rated & Largest Python Udemy Course + 56 Hrs + 200 Videos + Data Science bit.ly/Master_...
➡️ New C++ Programming Bootcamp Series for $9.99 : Over 23 Hrs + 53 Videos + Quizzes + Graded Assignments + New Videos Every Month bit.ly/C_Cours...
Welcome to my Observer Design Pattern Tutorial. I cover a lot in this tutorial including the Observer pattern, how to use it with threads and much more.
The Observer pattern is a software design pattern in which an object, called the subject (Publisher), maintains a list of its dependents, called observers (Subscribers), and notifies them automatically of any state changes, usually by calling one of their methods.

[@derekbanas]

Learn in One Videos for Every Programming Language Subscribe to Bookmark them: bit.ly/2FWQZTx C++ : kzbin.info/www/bejne/iKbFXn2pn7Kbjbs Python : kzbin.info/www/bejne/hGXQdq18ec-kqqM Java : kzbin.info/www/bejne/pF7bcqSZd6iqqZY PHP : kzbin.info/www/bejne/bYWpYWOef65qbrs MySQL : kzbin.info/www/bejne/r4HYZ6SMasesq5Y JavaScript : kzbin.info/www/bejne/nJvYapyfbb6mfdU C# : kzbin.info/www/bejne/oprWmqqLj6-Lp7M HTML5 : kzbin.info/www/bejne/oXXce4FtprZ4iqM CSS3 : kzbin.info/www/bejne/eYbbeZKojLh8Z80 JQuery : kzbin.info/www/bejne/eIi7mJp4YrlkoLM TypeScript : kzbin.info/www/bejne/Y4G1kIunjJ59gLc ECMAScript : kzbin.info/www/bejne/gJLOoJxmfJ2feMk Swift : kzbin.info/www/bejne/mnzEoJ2Fj5KUsJo R : kzbin.info/www/bejne/qWSpoK2Mm8lqp5Y Haskell : kzbin.info/www/bejne/ZmPCeWaCn9aAqJo Handlebars : kzbin.info/www/bejne/annYcqGDa8dlmpo Bootstrap : kzbin.info/www/bejne/naKydqKLh5qFfsk Rust : kzbin.info/www/bejne/i2Kod5p5g7F3eJo Matlab : kzbin.info/www/bejne/hIS2hZ6hgLeUmKs Arduino : kzbin.info/www/bejne/h4DCe5-wZtajetk Crystal : kzbin.info/www/bejne/eqmpgWCNn9anqcU Emacs : kzbin.info/www/bejne/f5LKk6lvbJl6orM Clojure : kzbin.info/www/bejne/mZqqqnuhedqDd6c Shell : kzbin.info/www/bejne/nqjVn6CHqtKnhtk Perl : kzbin.info/www/bejne/jXbKmXyOqJ15bMU Perl6 : kzbin.info/www/bejne/omHdgaqenLyHna8 Elixir : kzbin.info/www/bejne/pnOxgJSsh9SBgpI D : kzbin.info/www/bejne/qKi9d4ekm56Verc Fortran : kzbin.info/www/bejne/lZCVhpp8g76anJo LaTeX : kzbin.info/www/bejne/jJnQnH-ohM9_qdk F# : kzbin.info/www/bejne/mWjIf3eAg5xobrc Kotlin : kzbin.info/www/bejne/fpDSeJxuqtp3pqM Erlang : kzbin.info/www/bejne/f3bLqJZoppatfZY Groovy : kzbin.info/www/bejne/eGqbm5Zuncmob8k Scala : kzbin.info/www/bejne/equppWOPoL-ibq8 Lua : kzbin.info/www/bejne/n37ElKuQhrKDjtU Ruby : kzbin.info/www/bejne/epvManSCeMyZpq8 Go : kzbin.info/www/bejne/eXechGeHj9qJaZI Objective C : kzbin.info/www/bejne/a5bWgqSQfq9rack Prolog : kzbin.info/www/bejne/iarOqYqme9yAfdU LISP : kzbin.info/www/bejne/r562ometfdekr7c Express : kzbin.info/www/bejne/rnWmfJaEd6umq6s Jade : kzbin.info/www/bejne/omakiZaOdrVnqJo Sass : kzbin.info/www/bejne/rauWnHiigcd4fqc

[@123456wei]

Might I add.. gasp.

[@robl655]

Best programming tutorial series on the web. Derek, you helped me get my first job out of college. The knowledge I knew that got me my job I learned from your tutorials... not school (which I payed $$$ for).

[@derekbanas]

Rob L I'm very happy to hear that I could help that much :) Thank you for taking the time to tell me. Messages like this are the reason I keep making videos.

[@LukaPostruzin9]

Derek Banas I totally agree with Rob. Whenever I use or recognize some of the design patterns which I've learned through your video series, I immediately remember you and I'm feeling thankful. I'm also recommending these tutorials to everyone who needs help understanding design patterns. Greetings from Zagreb ,Croatia!

[@thehumanity0]

+Derek Banas Yeah these tutorials are amazing Derek. These and your algorithms tutorials are basically the equivalent of a computer science course at a prestigious university.

[@TheBondilein]

I am at a prestigous University and i am still watching this, top :)

[@curiousSloth92]

TheBondilein Can you confirm what The Humanity said? :)

[@javierguerrero9486]

7:57 "It's public not pubic" lol I cracked there.

[@nathanbivens2394]

7 years later and this content is still making a huge difference! Thank you, Derek!

[@amansingh1661]

10 years later and still making a huge difference.

[@marodonthemorone]

11 years and it still makes a difference

[@israelperezmasle6673]

12 years, and it's still as good

[@angryantaus8550]

I'm an electrical engineer with a background in hardware design and low level device driver and systems programming, mostly in ARM assembly and C. I was recently tasked with writing a much higher level OO project in C++ and have found that your tutorials are the only ones that thoroughly explain design patterns and other higher level software concepts. Thank you for these videos, they've helped me no end with my job.

[@PecPur]

14:08 The usage of observer pattern with threads is usually intended to allow subscribing/registering on a different thread from the one running the observer code i.e ensuring observer and subject/publisher don't run on the same thread. This wasn't demonstrated here (The threads were used for concurrency but both observer and subject execute in the same thread) and that confused me for some time. However the video still helped me in other ways.

[@derekbanas]

I'm extremely happy to hear that I was able to help :)

[@Deco1789]

Derek, i have a exam tomorrow about design patterns, and your channel/videos saved my life. Thank you so much man. You're make magic with your videos! Hope my channel about android help videos get cool like yours one day! Salutes from Brazil/Argentina!

[@raulzuniga4382]

I'm working my way through this series and I found this particular tutorial difficult to follow because the UML didn't match the actual code. Even for this small project it really helps to have a matching UML(it has a some 'implements' and 'has a' relationships). Once I updated the UML I rewatched the video and was able to follow along just fine.

[@derekbanas]

I'm very happy to have been of help with this topic that I really enjoyed covering :)

[@derekbanas]

You could do that. The design patterns aren't set in stone. There are many variations of them, so always feel free to do whatever makes your code most understandable

[@derekbanas]

Thank you :) I'm very happy you're enjoying the videos. I would have never thought a design patterns tutorial would be this popular

[@derekbanas]

You're very welcome :) It is my privilege to make them. It is very nice to help people

[@derekbanas]

Thank you for taking the time to tell me that :) It means a great deal to me that I was able to help!

[@derekbanas]

That is a very good point. Thank you for the input. I mainly write these programs out of my head and that is the reason why my naming isn't always perfect. I'm constantly trying to get better :)

[@talhumy]

I'm usually don't comment on video , special on programming video , but your tutorial is the best i have seen. thank you

[@derekbanas]

Thank you very much :) I appreciate you taking the time to tell me you liked it.

[@squidgeypea]

Thank you so much for this series of videos. You have saved me from failing at university, and I learned more in 20 minutes of your video than 2 hours in a lecture at uni.

[@derekbanas]

Thank you for taking the time to tell me I helped :) I greatly appreciate it

[@derekbanas]

Yes the Observer pattern is used heavily in the Swing framework.

[@derekbanas]

That is all I could ever ask for :) I'm just providing a service that I wish I had years ago. Thankfully the internet (KZbin) allows me to do what I do

[@TheRajmoney]

I don't know why, but this guy just explains everything perfectly. thanks Derek!!!

[@derekbanas]

Thank you for the compliment :)

[@derekbanas]

Thank you very much :) I'm trying to provide a complete software engineering degree online, but I still have a way to go. I'll keep at it

[@derekbanas]

I welcome criticism and you are indeed correct. Sometimes, or even most of the time it is hard to provide a perfect example that both explains the pattern and is easy to understand. That may say something about my own personal skills. I need to work harder to make better tutorials and I try to improve with each video.

[@derekbanas]

Thank you very much :) I have a link to all the code in the description for the video. Feel free to do anything you'd like with it. I don't require you to even mention that it is my code.

[@derekbanas]

Thank you :) Android pretty much uses MVC already. The interface is setup completely using the xml layout files. The Activity files act as the controllers. I code do a better job of modeling the Model better and separating everything better. Thank you for the input

[@derekbanas]

It is he view part of Model View Controller. Some people call MVC the Observer pattern, but that isn't by the book correct. Yes I have a separate tutorial on just the MVC pattern

[@istainblack]

I like the pace in these videos. I feel like a lot of other Comp Sci tutorials go very slow and I have trouble keeping interest. But never with Derek's videos!

[@derekbanas]

+istainblack Thank you :) I do my best to be different and not waste peoples time.

[@istainblack]

I salute you for that sir!

[@greg77389]

You don't consider 22 minutes slow?

[@derekbanas]

Not yet, but everything done in java can be done in c++ and c#. A c and c++ tutorial is in the works

[@derekdejonge2521]

Derek, next to your name, there is nothing better in this world than these videos.

[@derekbanas]

That's funny :) Thank you for the compliment

[@derekbanas]

Thank you :) I'm very happy to have been able to help.

[@THIRUMALAKIRAN]

This is the best resource available on design patterns. May be you can also share the codes on GitHub.

[@derekbanas]

You could definitely check if the observer is valid.

[@derekbanas]

I think you are looking for the Factory pattern. You use the Factory design pattern when you want to define the class of an object at runtime.

[@jonjohannson9536]

Derek, I appreciate so much the effort you put in your videos! I love the pace of them and that you mention the bigger context that was so often lost on the power point slides of university. I have started my first job and will have my (hopefully) last exam next week. Didn't even bother with the slides, when I saw that you have a series on design patterns.

[@derekbanas]

Thank you for the great compliments :) Congratulations on your last exam!

[@tivmego]

Thank you so so much. Now, I am confident, I will master DP after watching all of your DP tutorials. Do you have video tutorials on Java and Jee6?

[@slimanekaddour3054]

I am so surprised how come that the tutorial is free and I think the best one , we see that is very pedagogical, but there is some people who disliked?!?!?!? I am just wondering how can that happened ? Thank you sir for sharing your knowledge, respect god bless you .

[@derekbanas]

Thank you for the compliment :) May God bless you as well.

[@derekbanas]

Yes indeed. You have to register the observers so you can easily alert them to changes

[@bertobertoberto3]

Ah I see. Thank you. Well, I won't worry about the gui for now. Also, I'm planning to just download a bunch of stock symbols from a sector (technology) into an excel file, then read/write the excel data to the db. Then for each security, I will select 1 week's of daily data (open, high, low, close) and run "strategies" to decide buy/sell signal. A strategy consist of 1 or more module where a module is just for example (close > open), or (low > prev low). I'm also trying to figure the best...

[@derekbanas]

Je parle un peu français et utiliser un traducteur pour ce que je ne comprends pas. Merci d'avoir regardé :)

[@derekbanas]

I'm always glad to help if I can :)

[@lzhu12]

best tutorial for observer design pattern i'ever read. thx a lot :)

[@doonatsu2817]

Thank you very much for the good videos about design pattern, you are one of my all time best teachers.

[@btcstealth]

Exception in thread "Thread-0" java.lang.NumberFormatException: For input string: "197,01" at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1241) at java.lang.Double.valueOf(Double.java:504) at Observer2.GetTheStock.run(GetTheStock.java:63) at java.lang.Thread.run(Thread.java:724) And likewise for Thread 1 and 2.

[@derekbanas]

My Object Oriented Design tutorial may help you solve this problem. The first 2 videos should be enough. That is the process I follow for solving everything

[@derekbanas]

Merci. Combien de langues parlez-vous? Je pense que vous êtes le génie :)

[@derekbanas]

You could strip out the commas using a regular expression if it is found. Sorry I didn't cover that

[@derekbanas]

Hi, Sure I have links to the code for every design pattern on this one page newthinktank. com/videos/design-patterns-tutorial/ I'm glad you enjoyed them :)

[@kiratornator]

Thank you! I always look for your tutorials if i need help. They are always quick and to the point. Great Tutorial.

[@derekbanas]

Thank you very much :)

[@DaniloSouzaMoraes]

It's public not pubic... hahahahhahahaha

[@g4l3r4k]

Thanks for this great tutorial ! But for the record sometimes you have great talent to make things more complicated !

[@arthurmee]

Love these design pattern videos. Power to you Derek.

[@derekbanas]

It wouldn't be that different since C# looks almost exactly the same as Java. I plan on covering C# asap

[@rockYhre]

Thanks for another awesome video. A question: what have you enjoyed more, being in IT or finance? I'm thinking about these two career paths and will probably combine them but I wonder what you think as you were/are in both. Thanks!

[@ArneM7]

What do you think is the main difference between the decorator pattern and the mediator pattern? They just look the same.. But anyway great video!

[@derekbanas]

Java is definitely an OOP language. Everything in Java is an object. PHP isn't an OOP language. Sorry if I didn't explain that

[@bradyhuang5606]

19:50 println(stock + ": " + df.format((price + randNum))... should be println(stock + ": " + df.format((price))... since you already add the price at this line price = Double.valueOf(df.format((price+randNum))); otherwise the terminal output will be misleading.

[@MdSheraj]

Dude, I agree though I had to find hard to get to your comment!

[@derekbanas]

You're very welcome. AOP is implemented through the decorator pattern which I cover. I hope it helps

[@puneetkumaragarwal12]

liked ur videos..helped me to understand design principles...

[@derekbanas]

Try running it without putting commas in the number

[@DastardlyHopeful]

Rather than passing a stopGrabber object to each of the observers, could you make stockGrabber a singleton?

[@derekbanas]

Thank you very much :)

[@GhostNappa28]

This is the first educational video which made me laugh. ;D When you said "pubic" followed by "blah blah blah" I laughed harder than I should have :D Love your work! Keep it going! :)

[@derekbanas]

+Kaushik Sundar That's funny :) I'm happy you could find humor in my videos.

[@derekbanas]

Yes sorry about that

[@aquamicky]

Should talk more about design than just writing code and saying whats been written. Very bad usage of class names. StockGrabber, GrabStocks, GrabtheStock, Observer, StockObserver.. seriously?? It just confused me big time until i read the code independently to understand what you really wanted to achieve.

[@Neo_metallum]

He talked about the design at the beginning. If you can't follow up, it's not his problem

[@derekbanas]

Yes that is one of the things it is commonly used for

[@derekbanas]

Thank you :) Yes I agree. I wish I would have shown both. I was just doing my best to explain everything as simple as possible.

[@andrewabwoga]

Can you do a series on Domain Driven Design and how it applies to design patterns, OOP and generally programming?

[@derekbanas]

I made a series on the iterative design process in my object oriented design tutorials. I applied patterns in my refactoring tutorials.

[@vishwass9491]

awesome videos Derek .Really like your method of teaching.Its just what i wanted

[@derekbanas]

vishwas s Thank you :) I'm happy I could help.

[@coreymagin]

7:57

[@derekbanas]

There are many different ways to implement the different patterns

[@derekbanas]

Yes I should never use == for string comparison even when it would work. I'm sure at the time I had a weird reason to do it this way, but it was still wrong. Sorry about that

[@derekbanas]

Java is a fabulous language that is made perfect when combined with c / c++. PHP is good for what it does, but it definitely is not an oop language like people keep trying to tell me :)

[@derekbanas]

Funny :)

[@derekbanas]

Thank you :) I love covering the niche topics everyone else ignores. I'm glad you liked it!

[@derekbanas]

Sorry about that. Sometimes I struggle with whether I should just cover the pattern, or whether I should include an interesting example that makes the topic less boring. I revisit the observer pattern later using an easier to understand example

[@derekbanas]

To be honest I hated being a stock broker. I actually quit after I became a chartered financial analyst. I was more then likely in a bad office, but my experience was so terrible I left the industry. One reason why I left was my office / the home office lost me a $4 Million muni account because they wouldn't print up the portfolio! I love being in business for myself. I don't rely on anyone and I still get to play around with investing

[@rasenganm2116]

You are awesome! thank you very much!!! ;) you will definitely become one of the best channels on youtube

[@derekbanas]

+Dilyor Mihidinov Thank you for the compliment :)

[@derekbanas]

Thank you :) I appreciate the compliment.

[@NikolaZagorac]

Why did you give the Observer a object reference to the StockGrabber? It doesn't serve no obvious role and if it did, the observer can still be added to another StockGrabber and would probably cause lots of headache.

[@cas7449]

Hey Derek! Question, in GetTheStock you're using == to compare strings, isn't it better practice to use .equals()? And why did you opt for == instead? (: Cheers!

[@sangyeopha9555]

I agree too, "IBM".equals(stock); is the better than `==`

[@derekbanas]

I'm using a pseudo UML notation. I did this tutorial before I made my UML tutorial so I wanted to make sure people understood what I was doing. Sorry if that was confusing. If I could go back, I would have made the UML tutorial before this one

[@derekbanas]

Not many people know about me. I'm glad you found me and enjoy the videos :)

[@derekbanas]

It sounds like an observer would help

[@derekbanas]

You're very welcome :) Best of luck on the exam

[@ben8140]

Great explanation even today!

[@derekbanas]

I'm glad you like them. Don't worry about me. I have enough money

[@derekbanas]

I hope they help :) You're very welcome

[@derekbanas]

I'm very blessed to not have to do that anymore. I am very thankful to have had the opportunity to meet so many successful people when I was a broker. I wouldn't be where I am today without the advice they provided

[@TiaanHugovanderMerwe]

Dude, shouldn't you decrease the static count field for observer after one has been removed from the subject class?

[@derekbanas]

非常歡迎您

[@Huntinon]

Thx for the reply! Looking forward to your UML tutorial too!

[@derekbanas]

Thank you :) Im glad you found it useful.

[@derekbanas]

Thank you very much :) I do my best

[@derekbanas]

God bless you as well :) Thank you for the kind words. They mean a lot

[@MrNiceone99]

Great stuff but, kind of too fast for me. Not complaining because I like how you present. Reading a book on Design Pattern simultaneously helps me understand clearly. Thanks :)

[@derekbanas]

Thank you :) Sorry about the speed

[@ridwanulhasantanvir6456]

0:40 when to use observer 14:12 use threads

[@derekbanas]

Thank you :) You guys asked for them so I'm delivering

[@derekbanas]

You can store the observers in any way. You just need to maintain a list in one way or another. The patterns are just a guide. You can manipulate them in any way that works for your specific program

[@jaserq]

Thank you Derek .You are brilliant as allways. !

[@derekbanas]

Thank you for the nice compliment :)

[@derekbanas]

You're very welcome :) I'm glad it helped

[@derekbanas]

Thank you :) I love you also