29 lines
1.5 KiB
Markdown
29 lines
1.5 KiB
Markdown
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---
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title: SOLID Principle
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---
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## SOLID Principle
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A key programming princple which consists of the following conventions:
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(S)ingle Responsibility Principle
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(O)pen/Closed Principle
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(L)iskov Substitution Principle
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(I)nterface Segregation Principle
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(D)ependency Inversion
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Solid Responsibilty means a class should only do one thing (and preferably, do it well). So if a class is currently
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interacting with some SQL database, and also can generate a HTML page from them - the two functionalities should be seperated.
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Open/Closed Principle means you two never modify an existing class, but rather to extend them (does the word 'inheritance' ring
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any bells for you?).
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Liskov Substitution is one most often ignored. It means that whenever a code is written with use of base and child classes,
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it should be written as such that the program will never crash even if the child classes are substituted with their parent's.
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Suppose we have an Animal base class and a Dog\Cat child classes: It should not harm the flow if we write every Dog instance with
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an Animal's.
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Interface Segregation Principle means that when writing interfaces, it is better to write many ones each with very particular
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purpose, rather than having one interface to rule them all. Programmers are more likely to reuse small ones, and programs will
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be less cloggy with having to implement a big one.
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Dependency Inversion Principle means in (very) short, dont depend on concrete classes; try to use interfaces more.
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