Gain insights into software design patterns in C, explore their implementation, discover underlying principles, and learn to build a vocabulary for better communication and coding practices.

c.tar.gz

main+customer.c

main+customer.c-copy

watches

customers

observer

Reactor

Reactor-copy

observer-copy

Software design patterns are a valuable tool in any software developer's skill set. However, most design patterns are described in the context of an object-oriented programming language such as C++ or Java. The C language is sadly absent in the pattern literature. This course is here to change that by demonstrating that it is possible to use patterns in C programs and how it adds benefits to C programmers. You will learn why design patterns are more of a communication tool than technical solutions, and how patterns let you build and share a common vocabulary that simplifies communication.

The course presents a number of patterns and explains how to implement them in C. Each pattern is introduced via the problem it solves and the domains where the pattern can be used. We also discuss the underlying design principles as well as the trade-offs when applying the pattern. Finally, the course covers a set of coding idioms that will guide you when applying design patterns in C.

Software Design Patterns in C

Strategyis always implemented as a First-Class ADT.

State typically has a link to data owned by the calling context to initiate a state transition. 

Strategy represents a separation of concerns, whereas State doesn't.

From a 10,000 feet view, the structure of a State and Strategy implementation might look similar. However, the patterns differ in their intent. There's also one typical difference in the implementation of State vs Strategy:

From a 10,000 feet view, the structure of a State and Strategy implementation might look similar. However, the patterns differ in their intent. There’s also one typical difference in the implementation of State vs Strategy:

Extend the behavior of a function without modifying its implementation. Almost like magic. 

Let us modify a function without changing its external behavior. Also known as a **Refactoring**.

Follow established standards for network communication.

Code that follows the open-closed principle let us:

Code that follows the open-closed principle let us:

When we call a function, we are controlling its execution. We have made that function context dependent, meaning it is control coupled.

When we pass a flag to a function, we're creating a dependency on the inner logic of that function. If our assumptions change, we have to modify multiple parts of our program instead of encapsulating the behavior in one place. 

Control coupling results from overly detailed specifications that restrict the programmer's freedom to create the best possible solution.


The example in this chapter started with a naive implementation where we did a switch-case on an enum (```CustomerCategorycategory```). This approach created control coupling. Since control coupling is a common design flaw, it pays off to understand and avoid it. What's the main problem with control coupling?

The example in this chapter started with a naive implementation where we did a switch-case on an enum (<code>CustomerCategorycategory</code>). This approach created control coupling. Since control coupling is a common design flaw, it pays off to understand and avoid it. What’s the main problem with control coupling?

True, and it's an example of the benefits of a design following the open-closed principle. 

False, Strategy is for writing new code only.

Strategy is often a good approach when refactoring code duplication. You have multiple functions with very similar responsibilities. Extracting the varied concepts allows us to reuse the general algorithm. We can now represent each varied concept as a strategy passed to the general and reusable algorithm. True or false?


Strategy is often a good approach when refactoring code duplication. You have multiple functions with very similar responsibilities. Extracting the varied concepts allows us to reuse the general algorithm. We can now represent each varied concept as a strategy passed to the general and reusable algorithm. True or false?

Test your knowledge of the Strategy Pattern concepts with this quiz.

Introduction to Pattern in C

The First-Class ADT Pattern

The State Pattern

The Strategy Pattern

The Observer Pattern

The Reactor Pattern

Idiomatic Expressions

Conclusion

Quiz: The Strategy Pattern