XNA Service Injection Sample


ServicesDemo.rar [13 kb] – XNA GSE 1.0 Refresh Project (source only, the executable is pointless)


Finally, here it is!

In my last blog post I said I’d be doing a sample of what’s explained in it, so service dependencies and service injection in components and other services, in an XNA context. It actually worked in my own game for many weeks, but I just found the time and motivation to finish up my sample.

Details about the sample structure after the jump.

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Service Dependencies in Game Components

Update : See this post for a sample project!

Last summer I worked with Microsoft patterns & practicesGuidance Automation Toolkit, one of their software factories used for convenient Visual Studio 2005 extensibility. It imposed a strict but well-made service/component model not unlike XNA, but had some more stuff that I thought could become necessary in a big XNA game project; two of those being service dependencies and injection in components and services. So I went ahead an implemented them in an XNA context.

The principle is an extension to the current service/component model of XNA :

  • Components should be “pluggable” and react properly when removed from or appended to a project;
  • The only communication points between a component and its environment are the services it obtains from the game context.

This already works in a typical XNA project. My problem was that if a component needs a service to behave properly, it has no direct means of telling the game, so if the game can’t provide it, the component will throw a NullReferenceException when using the null service that the service collection returned.

Continue reading Service Dependencies in Game Components