Actions Shares. Embeds 0 No embeds. No notes for slide. Typescript design patterns applied to sharepoint framework - Sharepoint Satursday Madrid 1. What is this session about? More than , copies have been sold in English and in 13 other languages.
The authors are often referred to as the Gang of Four GoF. A design pattern isn't a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that can be used in many different situations.
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They are categorized in three groups: Creational, Structural, and Behavioral. Software professionals can immediately picture the high-level design in their heads when they refer the name of the pattern used to solve a particular issue when discussing system design. This pattern can be further divided into class-creation patterns and object-creational patterns. While class-creation patterns use inheritance effectively in the instantiation process, object-creation patterns use delegation effectively to get the job done. A singleton can maintain a state which is shared across the entire system.
Singletons abstract their internal workings from the rest of the system.
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If the physical location of configuration ever changes one would have to update many different files and lines of code. To solve this, developers implement a singleton for managing configuration. This allows an entire factory to be replaceable. Builder Builder pattern builds a complex object using simple objects and using a step by step approach.
This type of design pattern comes under creational pattern as this pattern provides one of the best ways to create an object.
A Builder class builds the final object step by step. This builder is independent of other objects. The idea on this example is to show how you can build a Complex object from single objects, a Meal from burger, fries, soda.
Suppose you have a Sharepoint List for Burgers, another list for Sodas, another one for desserts, and you want to build different Meals Menus , so this would be a perfect sample. Factory method Under some scenarios, a class cannot predict exactly what objects it will create, or its subclasses may want to create more specified versions of these objects. Then, the Factory Method Pattern can be applied. Advantage of Factory Design Pattern Factory Method Pattern allows the sub-classes to choose the type of objects to create.
It promotes the loose-coupling by eliminating the need to bind application-specific classes into the code. That means the code interacts solely with the resultant interface or abstract class, so that it will work with any classes that implement that interface or that extends that abstract class. A factory method is a method of a factory that builds objects From Book: Typescript Design Patterns Structural class-creation patterns use inheritance to compose interfaces.
Behavior design patterns Chain of responsibility A way of passing a request between a chain of objects Command Encapsulate a command request as an object Interpreter A way to include language elements in a program Iterator Sequentially access the elements of a collection Mediator Defines simplified communication between classes Memento Capture and restore an object's internal state Null Object Designed to act as a default value of an object Observer A way of notifying change to a number of classes State Alter an object's behavior when its state changes Strategy Encapsulates an algorithm inside a class Template method Defer the exact steps of an algorithm to a subclass Visitor Defines a new operation to a class without change These design patterns are all about Class's objects communication.
Behavioral patterns are those patterns that are most specifically concerned with communication between objects. The word SOLID comes from the initials of the five principles it refers to, including Single responsibility principle, Open-closed principle, Liskov substitution principle, Interface segregation principle and Dependency inversion principle. Those principles are closely related to each other, and can be a great guidance in practice. In , I started working on an application called Univjobs , a marketplace for Canadian students and recent-grads to find co-op jobs, gigs and entry-level jobs and internships.
The MVP was pretty simple.
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Students could sign up, create their profile and apply to jobs. Employers could sign up, post jobs, browse students and invite them to apply to the jobs they've posted. Since , we've iterated many times, adjusting and encorporating features based on feedback from students and employers such as job recommendations, interviews, an Applicant Tracking System and several portals to integrate with the existing platform developers, campus reps, etc.
Eventually, the codebase had became so large that adding new features on top of it took nearly 3x the amount of time it would have taken when I first started. Domain-Driven Design is an approach to software development that aims to match the mental model of the problem domain we're addressing. Initially conceptualized by Eric Evans who wrote the bible of DDD famously known as the Blue Book , DDD's primary technical benefits are that it enables you to write expressive , rich and encapsulated software that are testable, scalable and maintainable.
The Ubiquitous Language which is a fancy DDD term for the common language that best describes the domain model concepts can only be learned by talking with the domain experts. Once agreed upon, it enables developers to connect what the software implementation to what actually occurs in the real world. If we're building an app that helps recruiters hire talent, we need to spend some time understanding the domain language and processes that exist from the recruiters' perspective.
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Knowing the names of the constructs that we're about to model enables us to create rich domain models. There are huge payoffs in domain modeling.
Typescript design patterns for Sharepoint Framework Part 3 - Builder
When our code lines up with the real life domain, we end up with a rich declarative design that will enable us to make changes and add new features exponentially faster. Domain-Driven Design has a steep learning-curve. I won't lie about that. Domain-Driven Developers need to be comfortable with the following:. Object-Oriented Programming is not strictly necessary to be successful with Domain Driven Design, but it does go with the natural contours of the patterns Domain-Driven Design has established.
To be able to move quickly, DDD does require some fundamental knowledge of software design patterns. It's a lot harder to do DDD well if we make a mess.
Much of what makes frameworks so popular is that there is a pre-established way to do everything. When modeling the domain layer in DDD, there are already pre-established building blocks for every task. See here for the list of building blocks for DDD applications. In order to do DDD well, we need to keep the SOLID principles in mind, organize a central domain layer at the core of our Layered Architecture , and implement interface adapters to persistence, web and external technologies. We don't want these things to sully our domain model. We want to keep them at a distance so that we can isolate our domain and keep our unit tests fast.
I studied Java in high-school and University. This was scary for a 1st year University student learning how to program and. When I first picked up a book on Node. The community was much more interesting than the Java community to me as a musician and a gamer at the time. Like many others, we learned how to build Node. This was also the extent to which a large number of developers from my generation learned about software design. This works great for a large number of RESTful web backends, but for applications where the problem domain is complex, we need to break down the "model" part even further 1.
Entities live a life enabling them to be created , updated , persisted , retrieved from persistence, archived and deleted. These are a collection of entities are that bound together by an aggregate root. The aggregate root is the thing that we refer to for lookups.
No members from within the aggregate boundary can be referred to directly from anything external to the aggregate. This is how the aggregate maintains consistency. The most powerful part about aggregates is that they dispatch Domain Events which can be used to co-locate business logic in the appropriate subdomain. Because Domain Services are a part of the Domain Layer and adhere to the dependency rule , Domain Services aren't allowed to depend on infrastructure layer concerns like Repositories to get access to the domain entities that they interact with.
Application Services fetch the necessary entities, then pass them to domain services to run allow them to interact. We use repositories in order to retrieve domain objects from persistence technologies. Using software design principles like the Liskov Subsitution Principle and a layered architecture, we can design this in a way so that we can easily make architecture decisions to switch between an in-memory repository for testing, a MySQL implementation for today, and a MongoDB based implementation 2 years from now.
We'll want to create domain objects in many different ways. We might also want to create domain objects from templates using the prototype pattern or through the use of an abstract factory. Domain events are simply objects that define some sort of event that occurs in the domain that domain experts care about. However, in complex applications that can become very cumbersome think Gitlab or Netflix. Using domain services such as the ReferralFactoryService and application services such as the EmailService , Domain Events can be used to separate the concerns of the domain logic to be a executed from the subdomain it belongs.
Because it involves a lot of encapsulation and isolation of the domain model, it can take some time to accomplish. Depending on the project, it might be more worthwhile to continue building an Anemic Domain Model. If you're Junior Developer or getting started in the world of software architecture and design, I think you're on the right track. Domain-Driven Design has introduced me to a world of software architecture, patterns and principles that I might not have naturally started learning until much later.
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