课程: Programming Foundations: Design Patterns
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Extending behavior with composition
- [Instructor] Before we jump into a formal definition of the Decorator pattern, let's first get a conceptual feel for how Decorator works and in particular see how we might use composition to solve our problems. To do that, let's go back to our original beverage design. Now, let's say a customer wants to order DarkRoast with Mocha and Whip. So, let's start simply by instantiating a DarkRoast object, shown here. Let's also call this object our base object, the coffee itself. Next, the customer wants Mocha, so let's create a second object, a Mocha object and wrap it around or compose it with the DarkRoast object. We'll call Mocha a Decorator and as to the hint to the structure of all this, Mocha's type is going to mirror the type of the object that it's composed with. Which, in this case, is a beverage. So, Mocha also has type beverage. Note that means it also has a cost method, so keep that in mind. Now the customer…
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Creating chaos with inheritance4 分钟 12 秒
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Understanding the open-closed principle2 分钟 49 秒
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Extending behavior with composition2 分钟 29 秒
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Understanding the decorator pattern2 分钟 23 秒
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Using the Decorator pattern5 分钟 6 秒
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Challenge: The Decorator pattern40 秒
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Solution: The Decorator pattern1 分钟 22 秒
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