general principles, to four points:
• Separate out the things that change from those that stay the same.
• Program to an interface, not an implementation.
• Prefer composition over inheritance.
• Delegate, delegate, delegate.
following sections, we will look at each of these principles in turn, to see
what they can tell us about building software.
Separate Out the Things That Change from Those
That Stay the Same
Software engineering would be a lot easier if only things would stay the same. We
could build our classes serene in the knowledge that, once finished, they would continue to do exactly what we built them to do. Of course, things never stay the same,
not in the wider world and certainly not in software engineering. Changes in com-
puting hardware, operating systems, and compilers, combined with ongoing bug fixes and ever-migrating requirements, all take their toll.
A key goal of software engineering is to build systems that allow us to contain the
damage. In an ideal system, all changes are local: You should never have to comb
through all of the code because A changed, which required you to change B, which
triggered a change in C, which rippled all the way down to Z. So how do you achieve— or at least get closer to—that ideal system, the one where all changes are local?
You get there by separating the things that are likely to change from the things
that are likely to stay the same. If you can identify which aspects of your system design
are likely to change, you can isolate those bits from the more stable parts. When
requirements change or a bug fix comes along, you will still have to modify your code,
but perhaps, just perhaps, the changes can be confined to those walled-off, change-prone areas and the rest of your code can live on in stable peace.
But how do you effect this quarantine? How do you keep the changing parts from
infecting the stable parts?
Program to an Interface, Not an Implementation
A good start is to write code that is less tightly coupled to itself in the first place. If our
classes are to do anything significant, they need to know about each other. But what

當(dāng)前標(biāo)題：designpatterninruby
URL鏈接：http://aaarwkj.com/article8/gpisop.html

成都網(wǎng)站建設(shè)公司_創(chuàng)新互聯(lián)，為您提供外貿(mào)網(wǎng)站建設(shè)、搜索引擎優(yōu)化、網(wǎng)站收錄、品牌網(wǎng)站建設(shè)、軟件開發(fā)、網(wǎng)站制作

廣告

聲明：本網(wǎng)站發(fā)布的內(nèi)容（圖片、視頻和文字）以用戶投稿、用戶轉(zhuǎn)載內(nèi)容為主，如果涉及侵權(quán)請盡快告知，我們將會(huì)在第一時(shí)間刪除。文章觀點(diǎn)不代表本網(wǎng)站立場，如需處理請聯(lián)系客服。電話：028-86922220；郵箱：631063699@qq.com。內(nèi)容未經(jīng)允許不得轉(zhuǎn)載，或轉(zhuǎn)載時(shí)需注明來源： 創(chuàng)新互聯(lián)