Taming Software Dependencies with DI and IoC

with James Kovacs

Concepts

• Dependency Inversion (IoC)
• Higher levels should not rely on lower levels
• Abstraction
• Both should depend on something else (contract)
• Dependency Injection
• supply your dependencies to your objects
• Through the constructor or through setters
• Mandatory in constructor and optional in setters
• Problem:The presenter needs too know about the dependencies below
• Solution 1
• Write a default constructor that sets up the dependencies
• Solution 2
• Use and IoC Container
• At the core a dictionary
• Static gateway from JP is a basic example of this
• Windsor
• Does dependency resolution
• Autowiring
• Lifetime management
• Multiconfig options
• Run-time config
• Plug-ins

Dependencies

• If you pull out a class, how many other classes do you have to copy over too

Notes

• Don't fear the code
• Wizards constrain you
• MVC wizards is a good example
• .Net Pet Has a lot of coupling
• In DDD you use the language of the business
• Use Submit instead of Save for example
• Decorator Pattern
• Add functionality on top of and existing class
• such as logging
• Could we have done WSDBLink as a decorator?
• Use "`" in XML for Generics

Tools

• MS Unity DI tool
• Windsor - OSS DI Software
• StructureMap
• Spring.Net
• Bindsor
• Boo code to set up Windsor