Name: Java 教程 - 探討依賴反轉原則 (Java Tutorial - Exploring the Dependency Inversion Principle)
Uploaded: 2022-11-04T18:30:47.000Z
Duration: 5 min 12 s

- [Eric] The dependency and version principle

gives us guidance to not design our high-level modules

給我們的指導是，不要設計我們的高級模塊

because it advises us to think about designs

that depend on a lower level set of components.

We often think of the high-level components

that are commanding a set of low-level components

who are really carrying out all the real work.

哪些人真正在進行所有真正的工作。

是，它通常是緊緊地結合在一起

our high-level components to our low-level ones.

我們的高級別組件與我們的低級別組件之間的關係。

that high-level component and then to go reuse it

該高級組件，然後去重新使用它

with the totally different underlying implementation

that's something we really should be able to do.

這是我們真的應該能夠做到的。

tells us to think of this in a different way,

告訴我們要以不同的方式來思考這個問題。

by reversing the direction of this dependency.

通過扭轉這種依賴關係的方向。

首先，正如我們已經說過的，高級別模塊

actually both should depend on abstractions.

實際上，這兩者都應該依賴於抽象的東西。

And second, the principal offers that abstractions

actually details should depend on abstractions.

實際上，細節應該取決於抽象的東西。

Both of these statements require some explanation.

It has a click method that's called one user indicates

它有一個點擊方法，被稱為一個用戶表示

在一個較低的級別上調用電視。

the remote control click method has the logic to toggle

遙控器的點擊方法有邏輯，可以切換

between the on and off states by calling the turn TV on

通過調用 "打開電視"，在打開和關閉狀態之間進行切換。

So this design looks straightforward enough,

是以，這個設計看起來足夠簡單明瞭。

For starters, this remote control controls only televisions

對於初學者來說，這個遙控器只能控制電視

and more specifically the television represented

更確切地說，是以電視為代表的

What if we want to control another kind of television

如果我們想控制另一種電視呢？

or even another kind of device with an on-off switch?

It's not hard to notice that we have a high level component,

不難發現，我們有一個高層次的組成部分。

So according to our principal, that can't be good.

所以根據我們的校長，這不可能是好事。

但是，我們還能如何處理這個問題呢？

Let's think through what the high level policy

讓我們想一想，高水平的政策是什麼？

"It's the abstraction that underlies the application."

So, how's this for an improved high-level policy

那麼，這樣一個改進的高層政策如何呢？

that can control anything with an on off button,

可以控制任何有開、關按鈕的東西。

a TV, a light, a sprinkler system, and so on.

一臺電視、一盞燈、一個灑水系統，等等。

we're going to create an abstraction for an on-off device.

我們將為一個開關設備創建一個抽象的概念。

More specifically, we're going to create an interface

更具體地說，我們將創建一個接口

在關閉的設備上，支持兩種方法。

接下來，我們將有我們的遙控器

depend on that abstraction by composing our remote control

通過組成我們的遠程控制來依賴這一抽象概念。

And remember before the remote control dependent

on a concrete type, that television class.

在一個具體的類型上，即電視類。

So, now a remote control no longer depends

Instead, it actually depends on an abstraction

相反，它實際上取決於一個抽象概念

remember that our principal also tells us

that abstractions should not depend on details,

抽象的東西不應該依賴於細節。

rather details should depend on abstractions.

相反，細節應該取決於抽象的東西。

Well, let's examine the television class now

好吧，我們現在來研究一下電視類的問題

no longer does it expose its proprietary turn TV on

它不再暴露其專有的打開電視的功能。

So rather than our abstraction, the on-off device,

是以，而不是我們的抽象概念，即開關設備。

depending on the low level details of the television,

that is it's turned TV on and turn TV off methods,

那就是它的打開電視和關閉電視的方法。

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Java 教程 - 探討依賴反轉原則 (Java Tutorial - Exploring the Dependency Inversion Principle)

approach

improve

typically

specifically