Inversion of control
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www.jaftalks.com Introduction to the Inversion of Control
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Inversion of control design pattern and its implementation, dependency injection and service locator.
Transcript of Inversion of control
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Introduction to the
Inversion of Control
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AgendaWhat is a Dependency?Example Application High Level Architecture Inversion of ControlDependency InjectionService LocatorDependency Injection Pros/Cons Unity ContainerQuestions
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What is a Dependency?Some common dependencies include:
Application Layers Data Access Layer & Databases Business Layer
External services & Components Web Services Third Party Components
.NET Framework Components File Objects (File.Delete(…), Directory.Exists(…)) Web Objects (HttpContext, Session, Request, etc)
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Database
Data Access Layer
Which Depends OnBusiness Logic Layer
Which Depends On
User Interface
Depends on
Dependencies at a Very High Level
CI Server
BROKEN BUILD!
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The problem
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Code is tightly coupledDifficult to isolate when testingDifficult to maintain
If I change ComponentX how do I know what else it will affect? Did I break anything? If tests are in place they can be your safety net
What problems do dependencies create?
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Inversion Of Control
Don’t call me, I’ll call you
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Dependency Injection is an implementation of IoC
The ability to supply (inject) an external dependency into a software component.
Types of Dependency Injection: Constructor (Most popular)Setter Method
What is Dependency Injection?
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What is Dependency Injection?
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Dependency InjectionIn DI we have three ways of implementing
the same:Constructor way Setter wayMethod way
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Constructor Injection
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Setter Way
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Method Way
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DemonstrationLets See Some Code…
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ProsLoosely CoupledIncreases Testability (A LOT!)Separates components cleanlyAllows for use of Inversion of Control Container
ConsIncreases code complexitySome Jr. Developers find it difficult to understand
at FirstCan Complicate Debugging at FirstComplicates following Code Flow
Dependency Injection Pros & Cons
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Service Locator Form of the Inversion of Control pattern It allows classes to locate specific services they
are interested in without needing to know who implements the service.
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Service Locator
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Who will manage the Dependency Injection?
Containers !
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ContainerA container is an abstraction
responsible for object management, instantiation and configuration.
you can configure the objects using the container rather than writing client code like factory patterns to implement object management.
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Container
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Thanks For Listening. Mail: [email protected] Blog: http://www.jaftalks.com/ Twitter: http://twitter.com/jaftalks
“You should be pragmatic with any pattern,it's not necessary to be applicable for every situation”
Jaffal Hasan
Practical
