Book Review: Apprenticeship Patterns

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Here is a book which sounds different from its title: “Apprenticeship Patterns” but considering the complete title: “Guidance for the Aspiring Software Craftsman” would make some sense of what the book would be about. And then once you read the back cover of the book then I think its becomes much clearer of what you can expect in the book. So this is how I went about buying the book – I had never heard of this book before, found it in the bookstore and purchased it in no time. I did search for almost all the Computer related books on Flipkart, but didn’t find this. So someone who would want to purchase this book can go here. Ok, but I need to convince you to buy the book, so here is my attempt to do so:

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Moodle – Web based Virtual Learning environment

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Moodle is an Open Source Course Management System (CMS), also known as a Learning Management System (LMS) or a Virtual Learning Environment (VLE). Moodle is a free, open-source PHP web application for producing modular internet-based courses that support a modern social constructionist pedagogy. To work, it needs to be installed on a web server somewhere, either on one of your own computers or one at a web hosting company. Lot more information can be obtained from here.

There’s a better chance to grab the books available to learn about this platform from Packt publications, they are providing discounts on both their eBooks as well as printed copies. So you might be interested to know more about this here.

SOLID- Liskov Substitution Principle

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Liskov Substitution principle (LSP) states that,

Methods that use references to the base classes must be able to use the objects of the derived classes without knowing it

This principle was written by Barbara Liskov in 1988.

The idea here is that the subtypes must be replaceable for the super type references without affecting the program execution.

This principle is very closely related to Open Closed Principle(OCP), violation of LSP in turn violates the OCP. Let me explain:

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SOLID- Open Closed Principle

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Open Closed Principle (OCP) states that,

Software entities (Classes, modules, functions) should be OPEN for EXTENSION, CLOSED for MODIFICATION.

Lets try to reflect on the above statement- software entities once written shouldn’t be modified to add new functionality, instead one has to extend the same to add new functionality. In otherwords you don’t touch the existing modules thereby not disturbing the existing functionality, instead you extend the modules to implement the new requirement. So your code is less rigid and fragile and also extensible.

OCP term was coined by Bertnard Meyer.

How can we confirm to OCP principle?

Its simple- Allow the modules (classes) to depend on the abstractions, there by new features can be added by creating new extensions of these abstractions.

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SOLID- Single Responsibility Principle

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The Single Responsibility principle (SRP) states that:

There should never be more than one reason for a class to change.

We can relate the “reason to change” to “the responsibility of the class”. So each responsibility would be an axis for change. This principle is similar to designing classes which are highly cohesive. So the idea is to design a class which has one responsibility or in otherwords caters to implementing a functionality . I would like to clarify here that one responsibility doesnt mean that the class has only ONE method. A responsibility can be implemented by means of different methods in the class.

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