What's up geeks and welcome to the channel! If you're in the computer science domain you definitely have heard of design patterns before or even used a few patterns in practice with or without your knowledge but really what are design patterns? why were they created in the first place and who decided to create them? what is actually the main purpose behind design patterns? all these questions and more will be answered in this first video of our design pattern series to which later we will add more videos detailing each pattern on its own. As always and to better understand the concept at hand let's take a practical example and let's imagine a steak. You see I may have imagined a well done steak you may have imagined a medium done one someone else might have imagined a vegan steak, while ordering a steak at a restaurant, each one of us orders it differently we don't all necessarily have to order or eat our steak the same way and yet the cook that is preparing it, will take the same piece of meat or soy in addition to the way or policy of how we like our steak and prepare a delicious meal a different one for each one of us using the same piece of meat as a starting point To compare this to a computer program suppose we have a Chef class with a prepare() method This method can take a WellDoneInstruction object and in this prepare method the chef will know how to prepare a well-done steak but what about other ways of preparing a steak we will have to overload this method to take in a MediumDoneInstruction and a VeganInstruction Okay now our chef knows how to cook all the steaks we want Let's say this chef extended his knowledge and now knows of five additional ways to cook a steak should we add five more methods? Well let me suggest something else, why not replace all these methods with a single method that takes a steak cooking instruction and let all these classes inherit this one what do you think? Isn't that a better design for our Chef class You see this way, our class is closed for modification and open for extension which means that not only we won't have to add any more methods nor even touch our Chef class in the future but in addition to this when a new instruction is needed all we have to do is extend the SteakCookingInstruction class we created with this new instruction and the prepare method will handle it automatically Now because of our design, this chef apparently skyrocketed and decided to open a new branch for the restaurant So every time a new customer enters the restaurant the chef goes ahead and informs them of the opening date and details for the new branch but do you think that is the best approach to deal with such a scenario? Don't you think that instead of waiting for people to come in the chef should have instead messaged all his customers the details about the opening or even posted on social media and those interested would have showed up wouldn't his reach be far larger? In both previous scenarios the solutions I suggested hint at a specific pattern this pattern will not actually solve our problem and generate magically ready code for us but rather it will give us a description or template to follow a way of thinking that will help us solve these problems like a series of formalized best practices, steps that programmers have followed and used to solve common problems like the one we just encountered. Design Patterns best became known from the design patterns book by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides often referred to as the Gang of Four book published in the mid 90s. Now, this book details 23 design patterns which were split into three groups: Creational Patterns, Structural Patterns, and Behavioral Patterns. Creational patterns deal with the creation of objects Instead of you instantiating all objects very specifically and explicitly they give you more flexibility in how the objects are actually created Let's suppose that we have a class with 10 attributes but not every time we create an object based on this class we need to specify all 10 attributes sometimes you only need one, in other cases three or two, and sometimes eight or nine, in such cases we are left with two solutions and not quite the best out there: either to create a lot, like a lot, of overloaded constructors for our class or create one constructor that takes all arguments but then we will need to pass as null values the ones we don't require upon creation of our objects Well, design patterns will tell you wait, you have a third option follow the template provided by the Builder Pattern, a template widely used and tested by many developers out there Well if I were in your shoes I'd pick this last option. Structural patterns deal with how classes are actually designed with how things like inheritance and composition and aggregation can be used to provide extra functionality Let's consider that in our application we are storing book objects and these books well there's too many of them, like in the hundred thousand books of a library, or the books in all of amazon online store, and for some reason we need to represent each book by an object You see in this case we will have a bunch of book objects that will share the same attributes and by bunch I mean in the thousands which will have the same author, the same amazon physical storage location, same places it can be delivered to, same provider, etc. you got the idea and maybe the only attribute that will defer is the title itself and the price in some cases So why create for each book an object and consume all this amount of memory while at the same time if we follow the template specified by the Flyweight Pattern we will be able to minimize memory usage by sharing as much data as possible between our similar objects You see that is what design patterns are trying to do they are trying to provide us with a schema, a step-by-step definition or template to help us overcome development or architectural problems that others have faced before us. Finally, Behavioral patterns are specifically concerned with communication and assignment of responsibilities between objects as the program is running The two examples we gave at the beginning of our video can actually be solved using two different behavioral patterns one of them being the Strategy pattern Let's take a second example and suppose we realized that the state of an object in our application will be changed by a lot of other objects but we need to be able to undo the last change Well this can be done in many different ways and you are free to use any of them but there is a Memento design pattern that describes a simple proven approach. So to sum up, design patterns will speed up your development process by providing tested and proven development models At first you may not notice that you require the use of this pattern here or there or you may make use of it without even knowing but with time practice and hopefully with the help of our videos you will! So that's it for this video, I hope it was helpful, thank you guys for watching, take care and I will see you in the next one!