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转载：
Design Smells
If you are lucky, you start a project with a clear picture of what you want the system to be. The design of the system is a vital image in your mind. If you are luckier still, the clarity of that design makes it to the first release.
But then something goes wrong. The software starts to rot like a piece of bad meat. As time goes by, the rotting continues. Ugly, festering sores and boils accumulate in the code, making it more and more difficult to maintain. Eventually, the sheer effort required to make even the simplest of changes becomes so onerous that the developers and front-line managers cry for a redesign.
Such redesigns rarely succeed. Although the designers start out with good intentions, they find that they are shooting at a moving target. The old system continues to evolve and change, and the new design must keep up. The warts and ulcers accumulate in the new design before it ever makes it to its first release.
Fragility
Fragility is the tendency of a program to break in many places when a single change is made. Often, the new problems are in areas that have no conceptual relationship with the area that was changed. Fixing those problems leads to even more problems, and the development team begins to resemble a dog chasing its tail.
As the fragility of a module increases, the likelihood that a change will introduce unexpected problems approaches certainty. This seems absurd, but such modules are not at all unco妹妹on. These are the modules that are continually in need of repair, the ones that are never off the bug list. These modules are the ones that the developers know need to be redesigned, but nobody wants to face the spectre of redesigning them. These modules are the ones that get worse the more you fix them.
[ 本帖最初由 阿狗 于 2008-8-14 14:00 编纂 ] |
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