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Architectural Guidance for Building Mobile Apps Using Xamarin.Forms
- 1. Architectural Guidance for Building Mobile Apps Using Xamarin Forms Richard Taylor Vice President of Engineering SentryOne @rightincode – http://www.rightincode.com
- 3. Who is Richard Taylor? Full Stack Software Engineer Lives in Huntersville, NC Organizer of CLT Xamarin Developers Lead Organizer of Modern Devs CLT http://www.rightincode.com @rightincode Vice President of Engineering Huntersville, NC http://www.sentryone.com @sentryone @rightincode - http://www.rightincode.com
- 4. What are elements of a “good” software architecture? Separation of Concerns Single Responsibility Principle Loose Coupling Don’t Repeat Yourself (DRY) @rightincode - http://www.rightincode.com
- 5. How can we achieve a “good” software architecture? Use proven architectural styles Onion Architecture Use proven architectural/design patterns MVVM (Model-View-ViewModel) Inversion of Control Dependency Injection @rightincode - http://www.rightincode.com
- 6. Xamarin.Forms – Folder Structure @rightincode - http://www.rightincode.com Visual Studio Solution Explorer Reference Project: Tip Calculator
- 7. Xamarin.Forms Architectural Guidance – MVVM Design pattern that help facilitate the separation of the business and presentation logic from an applications user interface. The why.. Separation of Concerns Support unit testing of the view model/model independently of the user interface Easier maintenance @rightincode - http://www.rightincode.com
- 8. Xamarin.Forms Architectural Guidance – MVVM – cont. View Responsible for the user interface View Model Responsible for implementing of the properties and commands that the view binds to Notifies the view when state changes Coordinates all required interactions between the view and model @rightincode - http://www.rightincode.com
- 9. Xamarin.Forms Architectural Guidance – MVVM – cont. Model Represents the domain objects (data, business rules, validation) @rightincode - http://www.rightincode.com
- 10. Xamarin.Forms Architectural Guidance – MVVM – cont. Options for implementation Manual (review reference application) Frameworks MvvmCross MVVM Light Prism @rightincode - http://www.rightincode.com
- 11. Xamarin.Forms Architectural Guidance – Dependency Injection Enables the decoupling of concrete types from the code that depends on the types With DI, dependencies are provided by external facilities at runtime DI is a form of Inversion of Control @rightincode - http://www.rightincode.com
- 12. Xamarin.Forms Architectural Guidance – Dependency Injection – cont. DI helps improve testability DI does not require a container that houses the mapping between interfaces and their concrete types but DI containers are common @rightincode - http://www.rightincode.com
- 13. Xamarin.Forms Architectural Guidance - Validation Applications implementing the mvvm design pattern should perform validation in the view model and/or model ValidatableObject<T> approach… Properties of the view model/model that require validation should be of type ValidatableObject<T> that has validation rules defined in its Validations property Validation is done by calling the Validate method of the ValidatableObject<T> which executes the validation rules on its Value property @rightincode - http://www.rightincode.com
- 14. Xamarin.Forms Architectural Guidance – Validation – cont. ValidatableObject<T> approach cont. Errors are placed in the Error property of the ValidatableObject<T> The IsValid property of the ValidatableObject<T> is updated to indicate if the validation succeeded or failed For example, the entry view in Xamarin.Forms can be bound to the IsValid property and be notified if entered data is valid after validation and update the user interface accordingly @rightincode - http://www.rightincode.com
- 15. Xamarin.Forms Architectural Guidance - Navigation Support for navigation is built in and is considered view-first navigation View-first navigation has some weaknesses Tight coupling between views Difficult to coordinate navigation across views and view models (i.e. initiating navigation from a view model) Difficult to enforce business rules that impact navigation Unit testing navigation is very difficult @rightincode - http://www.rightincode.com
- 16. Xamarin.Forms Architectural Guidance - Navigation View model-first navigation alternative Can be achieved by implementing a custom navigation service or using one of the MVVM frameworks Placing the navigation logic in the view model Decouples views Improves testability by allowing easier unit testing of navigation Allows business rules to control navigation @rightincode - http://www.rightincode.com
- 17. Xamarin.Forms Architectural Guidance – Component Communications Typical communications between components are done using events which is a form of publish-subscribe communications Works but… Requires tight coupling between components Results in the extended lifespan of components until all references are removed @rightincode - http://www.rightincode.com
- 18. Xamarin.Forms Architectural Guidance – Component Communications MessagingCenter Class Implements the publish-subscribe pattern Allows components to communicate without having a reference to each other Allows components to be independently developed and tested Publishers send messages and subscribers listen for messages they are interested in Internally, the MessagingCenter Class uses weak references – it does not keep objects alive and allows them to be garbage collected @rightincode - http://www.rightincode.com
- 19. Xamarin.Forms Architectural Guidance – Unit Testing @rightincode - http://www.rightincode.com Code
- 20. Resources Repo: (code) https://github.com/rightincode/TipCalcPro Onion Architecture http://blog.thedigitalgroup.com/chetanv/2015/07/06/und erstanding-onion-architecture/ Inversion of Control https://martinfowler.com/articles/injection.html Unit Testing https://www.toptal.com/qa/how-to-write-testable-code- and-why-it-matters Pluralsight Building a Pragmatic Unit Test Suite Writing Highly Maintainable Unit Tests Advance Unit Testing @rightincode - http://www.rightincode.com
- 21. Resources Enterprise Application Patterns using Xamarin.Forms https://docs.microsoft.com/en-us/xamarin/xamarin- forms/enterprise-application-patterns/ Xamarin.Forms https://docs.microsoft.com/en- us/xamarin/#pivot=platforms&panel=XamarinForms @rightincode - http://www.rightincode.com