Design Patterns For Dummies®

Chapter 10. Coordinating Your Objects with the Command and Mediator Patterns

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Using the Command pattern to build a command toolkit

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Creating command queues and implementing an undo command

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Understanding the Mediator design pattern

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Connecting objects using the Mediator design pattern

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Building a Web site based on a mediator

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You’re consulting for GlobalHugeCo, the computer manufacturer, when the Chief Information Officer comes in, looks at a monitor on the wall, and says, “Uh oh.”

“What’s the problem?” you ask.

“We run servers for different regions of the world, and it’s mission-critical that we keep those servers operating.”

“And there’s a problem?” you ask.

The CIO looks wearily at the monitor on the wall and says, “We’ve got a 24-hour Crisis Center that handles calls from our major customers. If there’s a problem with the servers, we know about it instantly. However, there’s a problem with the Crisis Center.”

“And that is?”

“Our software is so confusing that the Crisis Center typically gets all bollixed up before it can handle any problem. If there’s a problem with the Asia server, our techs have to connect to the Asia server, run diagnostics, and disconnect again. Meanwhile, a problem with the Euro server might have come up, and they have to connect to the Euro server, reboot it, and disconnect. Then the U.S. server starts ...