This document discusses mobile app development architecture and design patterns. It covers the out-of-the-box approach using code behind, the model-view-viewmodel (MVVM) pattern, inversion of control (IOC), and command query responsibility segregation (CQRS). It also discusses tools like Fody, Polly, and Cimbalino Toolkit. Tips are provided on using universal apps, Windows 10 XAML, and developing cross-platform with Xamarin. The presentation ends with an invitation for questions.

1. MOBILE APP DEVELOPMENT
ARCHITECTURE & DESIGN PATTERNS
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2. Powered by
EXPERIENCE

3. ABOUT ME
Karol Szmaj
karol.szmaj@whallalabs.com
VP, CTO
+48 725 787 006
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4. Agenda
Out of the box approach
MVVM
Inversion of Control
Command and Query Responsibility Segregation
Tools & Tips
1
2
3
4
5
6 Questions
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5. DESIGN PATTERNS ARE SET OF
GUIDELINES NOT RULES
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6. Can be overkill for very simple application
Requires more time to bootstrap app
architecture
Disadventages
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Design Pattern Overview
Simplify maintenance
Separation of concerns
Minimize logic needed in UI
Enable testability
Reduce development time
Easy to customize apps
Adventages

7. OUT OF THE BOX APPROACH
CODE BEHIND
1
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8. Fast app prototyping
No time required for bootstraping application
Simple design: action + handler
Easy access to visual tree
Pros
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Out of the box approach
Code Behind

9. Large view classes
Breaks Single Responsibility Pattern
Hard to mantain in future
Poor code readability
UI customization can break logic inside view
Cons
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Out of the box approach
Code Behind

11. Creating small MVP of your product if there is an opportunity to refactor
Testing features
Small apps
When you should use it?
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When you shouldn’t use it?
Creating MVP without time to refactor
Enterprise apps
For apps with long-term support
Out of the box approach
Code Behind

12. MVVM – MODEL VIEW VIEWMODEL
2
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13. MVVM
Model-View-ViewModel
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Notifications
Data Binding
Commands
View ViewModel Model
UI Logic
Code Behind
Presentation
Logic
Bussiness Logic
And Data

14. Creating long term-support apps
When considering unit testing
When we need better code mantainability
When you should use it?
MVVM
approach
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When you shouldn’t use it?
For app testing purpose
When we don’t need testable bussines logic
When project is very simple (avoid architecture overengineering)

15. Lightweight
Developer controls everything
Implements: Command Patern, ViewModelBase, Messenger
Has IoC Container
MVVMLight
MVVM
frameworks
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16. WinRT focused
Support C#, C++/CX and HTML/JS
Validation, Conventions, Attached Events, Messenger, Logging
Very modular
Has IoC – Grace Container
StyleMVVM
MVVM
frameworks
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17. More complex, harder bootstrap
Better support for View Composition
Event aggregator
Conventions, Coroutines
Stable!
CaliburnMicro
MVVM
frameworks
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18. IOC – INVERSION OF CONTROL
3
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19. It’s not a library, framework or tool
It’s like a way of thinking, designing code and general guidelines
Dependency Injection is a set of practices that allow to build loosely coupled
applications
DI & IOC
What is it?
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20. Small components that are: independent, reusable, interchamgeable
We gain such benefits like: small classes (SRP), easy maintenance,
extensibility and testability
Dependency Injection is a set of practices that allow to build loosely coupled
applications
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DI & IOC
What is it?

21. IoC
Classic design
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ClassA ClassB
ClassC
ClassD
creates

22. IoC design
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ClassA ClassB
ClassC
ClassD
requires
Container
Model
Instance of ClassA
GetInstance

27. CQRS
4
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28. Query stands for reading
Commands stands for writing
Command/Query Responsibility Segregation (CQRS) is the idea that you
can use a different model to update information than the model you use to
read information (web experience).
CQRS
What is it?
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29. CQRS
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30. ALL OF THIS TO PROVIDE
SCALABILITY & A CONSISTENT
VIEW OF THE DATA.
[WEB]
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31. Classes are responsible for doing one particural job
Easy testability, extensibility and readability
Easy to mantain
Can be shared via multiple projects (portable)
Adventages of CQRS in mobile application:
CQRS
Why do we need it?
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38. TOOLS & TIPS
5
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39. MrAdvice – AOP tool
MethodTimer – decorates method with a timer
NullGuard – useful for Defensive Programming
Visualize – DebuggerDisplay weaver
Fody is a extensible tool for weaving .net assemblies
Tools - Fody
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40. Polly is a .NET 3.5 / 4.0 / 4.5 / PCL (Profile 259) library that allows
developers to express transient exception handling policies such as Retry,
Retry Forever, Wait and Retry or Circuit Breaker in a fluent manner.
Tools - Polly
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await Policy
.Handle<SqlException>(ex => ex.Number == 1205)
.Or<ArgumentException>(ex => ex.ParamName == "example")
.RetryAsync()
.ExecuteAsync(() => DoSomethingAsync());

41. Cimbalino Toolkit is a set of useful and powerful tools that will help you build
your Windows Platform applications.
Tools - Cimbalino
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Supports:
Windows Phone Silverlight 8.0+
Windows Phone / Windows Store 8.0 (WinRT)
Universal App Platform (Windows 10)

42. What do we get?
Tools - Cimbalino
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Behaviors
Converters
Extension classes
Services
Helpers

43. What do we get?
Tools - Resharper
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Better IntelliSense
Great refactor tool
XAML Support
R# just rocks!

44. Better to:
Tip #1 – Universal Apps 8.1
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Separate styles and templates using stalellite libraries
Add ViewModels to portable library NOT to shared project
Design your app architecture to support multiple platforms like Xamarin
Design your project to support adapter pattern
Throwing exceptions from layers is not the best way to handle errors

45. What do we get?
Tip #2 – Windows 10 XAML
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Improved XAML performance
x:Bind – faster compiled binding
Adaptive design
.Net Native

46. App design guidelines
Tip #3 – Xamarin
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Design your code logic to be not dependant on specific platform
Test your code on each platform
Don’t code without thinking about the problem
Design your code to be simply and readable.
Don’t overengineer your app

47. QUESTIONS?
Karol Szmaj
karol.szmaj@whallalabs.com
VP, CTO
+48 725 787 006
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