Your videos are one of the coolest things I found on youtube. Every time they present a design pattern in my university I watch one of your videos. You came to Argentina. Thank you! (Sorry my english is bad)
Awesome, I really love your way of explaning things. BTW you helped me a lot to understand a lot of concepts and terms which helped me to pass the technical exam and interview of a new job. thanks a lot Christopher
Youre amazing man, I wish you could be my academician for my patterns lecture. 2 Days later I got Final exam and I finally understood how do many design patters work. Thanks for all, I wanna meet you some day cause your energy is perfect.
Kudos for pointing out that Template Method is a good case of Open/Closed principle usage. My understanding is that in ASP NET WebForms they use Template Method so that developer could hook his code into page life cycle, because developer inherits his code-behind class from base Page class there. Even though they call it "events", developer doesn't have to use events subscription mechanism. But developer doesn't have to add "override" either. Ok, I'm not sure if that's canonical Template Method pattern in action.
Thank you so much for your amazing work! Really has helped me to grasp the concept of design patterns and see how useful they are. Thanks to you, my code became cleaner, more universal and more efficient. This is definitely the best design-patterns-explaining channel I have come across.
The whole point of this pattern is to be able to do Record r = new User; r->save(); so records are uniformely treated. User u = new User doesn't show the power of the pattern.
in the definition of template pattern, they have used word "operation" because 'operation' term is equivalent to class method. And because we are only templating a method and not a whole class, author might have thought to emphasis more on it.
The funny thing is that when I learned about abstract classes in my very junior days, I thought they were meant for that very reason, provide base implementations and hooks. Then I learned about this pattern and I was like "wait, isn't it obvious?"
Hehe :) In some sense it indeed is. And in some sense I guess one could argue that all of the GoF design patterns are more or less obvious ideas that anyone who carefully contemplates OO will come up with on their own. But whether these ideas were then given names so that we can more easily talk about them or so that authors can sell more books I do not know :) :) Thanks for watching and for sharing! Interesting and relevant perspective.
Oh absolutely, a big part of pattern usefulness is to create a common language to share ideas of design (or make money), but still they're also a way of teaching usage and put some structure for those who are lost in the big mess of possibilities that is an OO language. Everyone is different but when I learned about those around Y2K this one was basically the only one where I sort of had made gotten the idea of "wait, is there any other way ?"
I remember using this pattern (without knowing it's name) a while back while making a tweening system. The abstract tweening class had a method that calculated a 0-1 clamped value along a curve, and then called an abstract method for concrete tweens to implement using that clamped value as a parameter. In the end each concrete tween had a simple Evaluate(float t); to control animation. It worked great! Great tutorial series by the way! You are a great teacher :)
Template pattern could be substituted with a Strategy: A class "A", which implements a 'Template()' method only, and has a dependency on other classes that are needed in that method. They would implement "INeededOperations". So the usage would be: INeededOperations neededOps1 = new ConcteteOperations1(); //Needed by class A operations implemented. object a = new A(INeededOperations); //dependency injected with needed operations. a.Template(); //actual method called, which used to be an abstract template method. This way, only Class A is there and no other variations of class A exist because we need to use the 'Template()' method. But multiple variations of the INeededOperations are implemented. Instead of the abstract class using ghost functions, this way 'real' injected functions would be used. By the way, I totally love these series. Way to go Christopher!
A good example of template pattern would be any lifecycle component. e.g. reactjs component or android component where frameworks calls lifecycle hooks like `onCreate` `onDestroy`. Also I guess most of this use cases break single responsibility principles. As your `User` model is responsible for holding data and saving it. 38:40 good use of `trim`
It will absolutely come :) If I would guess I would however say that it probably drops after New Years rather than before. But I hope that doesn’t cause any troubles for you 🙂🙂 Thanks for the encouragement!
I like the way you explain the design patterns. Just a suggestion, you can use {A} for abstract classes and methods instead of italics or other styles as UML for Java programmers book suggests. By Robert C. Martin.
Chris, the subtitles (cc) in this video is being detected as Dutch. Could you please change the cc setting to English so that non native English speakers can follow along better? I think it must be a simple setting in your RUclips studio. Thanks!
Do I get that right? Hmmm... The Strategy pattern abstracts over different algorithms that have a somewhat same behaviors but (possibly) strongly different structure (I think about sort algorthms "bubble sort" vs. "sorting networks"). The TemplateMethod Pattern would more for a specifically structured algorithm, that have only view portions different - like... a bubblesort where you templatized the type and the type specific swap of the things that are sorted.
Firstly Thanks for your videos they are amazing to clear concepts up . I am actually from Database background and learning Object oriented programming ( Java mostly ) out of interest . One question I had - what is this virtual keyword mentioned in the concept of hooks while implementing the Template method pattern ?
23:27 we can even use strategy pattern an other way inject strategy and Template Method will call *strategy.DoOperationsInSteps(this)* it admire composition over inheritance.
I guess not if you think about the responsibility of the template method as "organise the structure of the algorithm correctly". Which I guess comes back the whole discussion about when the template method would be an appropriate pattern - it only makes sense if the algorithm has a predefined structure which has to be preserved. At least, that's how I see it.
few things are misleading/wrong, In strategy pattern behavior is injected in run time, i.e. the iAlogo's Concrete class has a behavior; whereas in template method a template is extended to get a new behavior at the compile time.
Regarding differences between Bridge and Strategy, isn't it that in Bridge, the Implementor part is more like Value Objects, whereas Strategy works with services/algorithms? I am just learning about patterns these days so it might be pretty dumb what I just said.
24:00 I think I agree, that composition should be favored over inheritance, but I have a question regarding this case. In a scenario where we want to use Template Method Pattern, but we want to have the ConcreteClass inherit from say class Animal, couldn't we just let AbstractClass inherit from Animal and then ConcreteClass inherit from AbstractClass as usual, or is that problematic? (This is regarding the "spot for inheritance" 24:36) I understand that composition can be used way more freely than inheritance in languages that do not support multiple inheritance (like Java), but at least for the Template Method Pattern, I don't yet see how letting AbstractClass inherit from the Class you wanted ConcreteClass to inherit from is an issue. Also it feels like there should be a way to have something like the Template Method Pattern in interfaces that isn't a Startegy Pattern, but I can't really think of it right now... Awesome video btw, much support :)
Can you share some detailed thoughts on "Composition over Inheritance". Just a thought, can't we do what template pattern does using Decorator and Strategy if I am sticking to Composition over inheritance principle. Though I think it would be asking too much from the end user to use features of Abstract Class (used in your example.)
Never read about the Template Pattern, but the moment Chris read the definition I paused the video for a minute to think and came up with the exact uml diagram and the code. The rest of the video was just like reinforcing my idea...guess I am really good at this stuff
Simple application of template method pattern is in Instagram where template is the same but content(image, reel, etc) are different. PS: This is just an example.
Funny. I’ve been building a way to run optimizations on models where exact implementations could vary. I thought I was using the strategy pattern, like a boss, turns out I created a template function letter by letter. Including the lifecycle hooks. The more I learn about design patterns, the more I realize it’s all just common sense. If you understand object orient programming - *really* understand - you know design patterns.
I'm not getting the whole "hook" aspect. Why would you have a concrete method that's empty? If the sub class doesn't override the empty hook method, you have no implementation anywhere that's ran. What's that point of calling the hook method from the templateMethod() if the hook method may never provide any behavior? Wouldn't templateMethod() have to check if an implemented hook method somewhere, did something.
I have a very bad habit of watching videos at 2xSpeed; and while watching, it seems like you are having strokes..... joke a part.. Good job, keep it up
Really on the long side man. I feel like the design pattern could be expressed much more succinctly. For example on Singleton, I could say that the theory is having only one object instantiated at a time. That in multithreaded applications it becomes harder. Then speak of when it should be used and why not. Then at the end show a tiny bit of UML and pseudocode. Just my two cents
I disagree. Short explanations omit a lot of underlying concepts and personally I find it great, that Chistopher describes the patterns clearly and in details. I also like the fact, that the most important ideas are repeated several times during the video, as it helps to remember better. Christopher, thank you for these great videos, they're so much better than our university lectures! :)
Your videos are amazing but I wish you would just compress them a tiny bit... I feel like you could just be more efficient and clear. By the time I finish though, it's really clear. I just need to cram for exams and 50mins even at 2x the speed is a lot of time :p
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How someone can be relevant after 6 years!! Amazing!!
If I can tell you how much I appreciate the work you are doing... you will not believe me. Please continue and don't stop.
Used these videos 6 year back to clear exams... still use them as a reference at work!! Amazing content!!
Please continue with this serie, your videos are awesome!
Your videos are one of the coolest things I found on youtube. Every time they present a design pattern in my university I watch one of your videos. You came to Argentina. Thank you! (Sorry my english is bad)
This was a fantastic lecture. The lecturers at my university could learn a thing or two from you about how to teach. Many thanks!
Awesome, I really love your way of explaning things. BTW you helped me a lot to understand a lot of concepts and terms which helped me to pass the technical exam and interview of a new job.
thanks a lot Christopher
Man you are Genius just when i was thinking this look similar to Strategy pattern you covered that part just then.
I use "Ruby On Rails" on daily basis. Didn't know it's very neat use of Template Method Pattern. Thanks :)
Youre amazing man, I wish you could be my academician for my patterns lecture. 2 Days later I got Final exam and I finally understood how do many design patters work. Thanks for all, I wanna meet you some day cause your energy is perfect.
you are the best who explain design pattern , thank you man ......
Kudos for pointing out that Template Method is a good case of Open/Closed principle usage. My understanding is that in ASP NET WebForms they use Template Method so that developer could hook his code into page life cycle, because developer inherits his code-behind class from base Page class there. Even though they call it "events", developer doesn't have to use events subscription mechanism. But developer doesn't have to add "override" either. Ok, I'm not sure if that's canonical Template Method pattern in action.
Thank you so much for your amazing work! Really has helped me to grasp the concept of design patterns and see how useful they are. Thanks to you, my code became cleaner, more universal and more efficient. This is definitely the best design-patterns-explaining channel I have come across.
Thank Christopher for creating this tutorial. It's make me more understand about design patterns: )
I’m glad to hear :)
You are the man, I've never looked forward to a lecture before
Your videos are amazing!! Thanks a lot! This series has helped me a lot in understanding Design Patterns! :D
I love your accent. In addition you are my hero when it comes to design patterns
Awesome very clearly explained and great to use a board to explain
This one was pretty complex for me up until the code example. Thanks for adding that one!
And as always thanks!
The whole point of this pattern is to be able to do Record r = new User; r->save(); so records are uniformely treated. User u = new User doesn't show the power of the pattern.
in the definition of template pattern, they have used word "operation" because 'operation' term is equivalent to class method. And because we are only templating a method and not a whole class, author might have thought to emphasis more on it.
I want to see this guy code amazing explanation please make a video where you share some problems you have solved at your workplace
Well done, Christopher! As always! BTW, do you plan to continue your series of videos about the books you have finished to read?
Thank you :) Much appreciated :) Do you mean the videos on non-programming books?
Christopher Okhravi yes, this is exactly what I meant.
The funny thing is that when I learned about abstract classes in my very junior days, I thought they were meant for that very reason, provide base implementations and hooks. Then I learned about this pattern and I was like "wait, isn't it obvious?"
Hehe :) In some sense it indeed is. And in some sense I guess one could argue that all of the GoF design patterns are more or less obvious ideas that anyone who carefully contemplates OO will come up with on their own. But whether these ideas were then given names so that we can more easily talk about them or so that authors can sell more books I do not know :) :) Thanks for watching and for sharing! Interesting and relevant perspective.
Oh absolutely, a big part of pattern usefulness is to create a common language to share ideas of design (or make money), but still they're also a way of teaching usage and put some structure for those who are lost in the big mess of possibilities that is an OO language. Everyone is different but when I learned about those around Y2K this one was basically the only one where I sort of had made gotten the idea of "wait, is there any other way ?"
@@ChristopherOkhravi Yeah I think everyone at some point has accidentally reinvented a design pattern before they knew what a design pattern was
Another great video, thanks for sharing
That was absolutely awesome!!!! VERY VERY THANKS! p.s. i am eagerly waiting for your UML basics or maybe tips video.
Amazing explanation. Hats off to you...
I totally agree with your point about the Strategy Pattern! very well explained
I remember using this pattern (without knowing it's name) a while back while making a tweening system. The abstract tweening class had a method that calculated a 0-1 clamped value along a curve, and then called an abstract method for concrete tweens to implement using that clamped value as a parameter. In the end each concrete tween had a simple Evaluate(float t); to control animation. It worked great!
Great tutorial series by the way! You are a great teacher :)
Great video! Thanks very much!
Very good video. Cleared the concept of template method. Keep it up
I have been using this one for years without even knowing it
Excellent explanation, helped a lot. thanks btw
Appreciate your efforts for providing this quality content !
Awesome explanation. You are my hero
Template pattern could be substituted with a Strategy:
A class "A", which implements a 'Template()' method only, and has a dependency on other classes that are needed in that method. They would implement "INeededOperations".
So the usage would be:
INeededOperations neededOps1 = new ConcteteOperations1(); //Needed by class A operations implemented.
object a = new A(INeededOperations); //dependency injected with needed operations.
a.Template(); //actual method called, which used to be an abstract template method.
This way, only Class A is there and no other variations of class A exist because we need to use the 'Template()' method. But multiple variations of the INeededOperations are implemented.
Instead of the abstract class using ghost functions, this way 'real' injected functions would be used.
By the way, I totally love these series.
Way to go Christopher!
Thanks Chris! Keep up the great work.
It must has taken a lot of effort to prepare and edit the video, thank you!
A good example of template pattern would be any lifecycle component.
e.g. reactjs component or android component where frameworks calls lifecycle hooks like `onCreate` `onDestroy`. Also I guess most of this use cases break single responsibility principles. As your `User` model is responsible for holding data and saving it.
38:40 good use of `trim`
If possible I would like to see a video of the design pattern called mediator. Thanks for sharing your knowledge!
It will absolutely come :) If I would guess I would however say that it probably drops after New Years rather than before. But I hope that doesn’t cause any troubles for you 🙂🙂 Thanks for the encouragement!
@@ChristopherOkhravi Did we add this? What is the name of the video title if it's part of this playlist?
really nice explanation about strategy vs template
Appreciated.
Awesome video. Thank you so much again :)
I hope that in the future you will cover all patters from the GoF instead of just the ones covered in the heads first book
Thank You, you saved my exam
Good Job, Chris! Thanks!
like your passion for teaching !! thanks :)
"HERO POSTER" haha... I like it :)
Nice video as always(especially very good example!) :) btw, do you have podcast channel?
I like the way you explain the design patterns. Just a suggestion, you can use {A} for abstract classes and methods instead of italics or other styles as UML for Java programmers book suggests. By Robert C. Martin.
Thank you for the great suggestion! Not sure what I was thinking when I tried to write in italics :D
@@ChristopherOkhravi Handwritten italics 😅
Chris, the subtitles (cc) in this video is being detected as Dutch. Could you please change the cc setting to English so that non native English speakers can follow along better? I think it must be a simple setting in your RUclips studio. Thanks!
Like before watching
I was waiting for this pattern
Do I get that right? Hmmm... The Strategy pattern abstracts over different algorithms that have a somewhat same behaviors but (possibly) strongly different structure (I think about sort algorthms "bubble sort" vs. "sorting networks"). The TemplateMethod Pattern would more for a specifically structured algorithm, that have only view portions different - like... a bubblesort where you templatized the type and the type specific swap of the things that are sorted.
thank you so much, this videos are so helpful!!
Firstly Thanks for your videos they are amazing to clear concepts up .
I am actually from Database background and learning Object oriented programming ( Java mostly ) out of interest . One question I had - what is this virtual keyword mentioned in the concept of hooks while implementing the Template method pattern ?
Thank you so much
Good Job!!!
Thank you!
23:27 we can even use strategy pattern an other way
inject strategy and Template Method will call
*strategy.DoOperationsInSteps(this)*
it admire composition over inheritance.
Thank you, Christopher! I have one question though, does the template method violate SRP actually?
I guess not if you think about the responsibility of the template method as "organise the structure of the algorithm correctly". Which I guess comes back the whole discussion about when the template method would be an appropriate pattern - it only makes sense if the algorithm has a predefined structure which has to be preserved. At least, that's how I see it.
nice explanation dude! thanks a lot!
great explication !!!
I believe this pattern can be implemented without inheritance! Anyway, your videos are great.
2:18 Cracked me "This is aah"
few things are misleading/wrong, In strategy pattern behavior is injected in run time, i.e. the iAlogo's Concrete class has a behavior; whereas in template method a template is extended to get a new behavior at the compile time.
Super usefull thank you so much!
awesome!
Become teacher on UDEMY and let others understand the patterns. I would be the first to buy the course.
Regarding differences between Bridge and Strategy, isn't it that in Bridge, the Implementor part is more like Value Objects, whereas Strategy works with services/algorithms? I am just learning about patterns these days so it might be pretty dumb what I just said.
24:00 I think I agree, that composition should be favored over inheritance, but I have a question regarding this case.
In a scenario where we want to use Template Method Pattern, but we want to have the ConcreteClass inherit from say class Animal, couldn't we just let AbstractClass inherit from Animal and then ConcreteClass inherit from AbstractClass as usual, or is that problematic? (This is regarding the "spot for inheritance" 24:36)
I understand that composition can be used way more freely than inheritance in languages that do not support multiple inheritance (like Java), but at least for the Template Method Pattern, I don't yet see how letting AbstractClass inherit from the Class you wanted ConcreteClass to inherit from is an issue.
Also it feels like there should be a way to have something like the Template Method Pattern in interfaces that isn't a Startegy Pattern, but I can't really think of it right now...
Awesome video btw, much support :)
Can we say Template pattern lies in between bridge pattern and strategy pattern, in terms of coupling?
Can you share some detailed thoughts on "Composition over Inheritance". Just a thought, can't we do what template pattern does using Decorator and Strategy if I am sticking to Composition over inheritance principle. Though I think it would be asking too much from the end user to use features of Abstract Class (used in your example.)
Excellent :) .....
:) I’m glad to hear. Thanks for watching :)
Never read about the Template Pattern, but the moment Chris read the definition I paused the video for a minute to think and came up with the exact uml diagram and the code. The rest of the video was just like reinforcing my idea...guess I am really good at this stuff
Simple application of template method pattern is in Instagram where template is the same but content(image, reel, etc) are different.
PS: This is just an example.
marking save() method as final makes more consistent .
Can we say the bridge method is a generalization of the Template Method?
Funny. I’ve been building a way to run optimizations on models where exact implementations could vary. I thought I was using the strategy pattern, like a boss, turns out I created a template function letter by letter. Including the lifecycle hooks. The more I learn about design patterns, the more I realize it’s all just common sense. If you understand object orient programming - *really* understand - you know design patterns.
hook method and method overriding are the same term that you are referring to or they are different things ?
brilliant!
can you explain dependency injection concept in a separate video please....
How is this different from a simple abstract class or an interface?
I'm not getting the whole "hook" aspect. Why would you have a concrete method that's empty? If the sub class doesn't override the empty hook method, you have no implementation anywhere that's ran. What's that point of calling the hook method from the templateMethod() if the hook method may never provide any behavior? Wouldn't templateMethod() have to check if an implemented hook method somewhere, did something.
Great
22:20 Nice bonk XD
I have a very bad habit of watching videos at 2xSpeed; and while watching, it seems like you are having strokes..... joke a part..
Good job, keep it up
"Template method defines skeleton of algorithm in an operation" I think here opration = method. I heard these words interchangably in my classes.
17:55 uuuaahh :P :P
Please cover Chain of responsibility pattern i have tough time understanding it only you can help :)
Also Mediator, Visitor and Memento please
22:24 Ahaha love it!
rule1 of software developer. It's never going to change= next week will change
what it remains: chain of responsability, Command, Interpreter, Mediator, Memonto, Visitor design patterns. please please please.
Command is already done. You can find it here ruclips.net/video/9qA5kw8dcSU/видео.html
Huh, here’s a pattern I’ve used without knowing it.
Don't call me, I will call you.
Good conceptual info but you can find better real time example.
Really on the long side man. I feel like the design pattern could be expressed much more succinctly. For example on Singleton, I could say that the theory is having only one object instantiated at a time. That in multithreaded applications it becomes harder. Then speak of when it should be used and why not. Then at the end show a tiny bit of UML and pseudocode. Just my two cents
Super good two cents. Much appreciated :) I need to learn to control my ramblings and rants :) Thanks for watching and for the feedback 🙏 😊
I disagree. Short explanations omit a lot of underlying concepts and personally I find it great, that Chistopher describes the patterns clearly and in details. I also like the fact, that the most important ideas are repeated several times during the video, as it helps to remember better.
Christopher, thank you for these great videos, they're so much better than our university lectures! :)
@@oceanhugstheshore Agreed!
Your videos are amazing but I wish you would just compress them a tiny bit... I feel like you could just be more efficient and clear. By the time I finish though, it's really clear. I just need to cram for exams and 50mins even at 2x the speed is a lot of time :p
HoF, functional programming is so much simpler...
Paterns exist also in functional programming. Doesn't matter if is an object or function . Also you need sometimes use inheritence
1k likes :)
All your other vids are good, but this one too wordy so plz start at 42:00
Captain Jack Sparrow.!! 😉😂