Refactoring: Improving the Design of Existing Code Chapter 6 : A first Set of Factorings Chapter 7 : Encapsulation Summary

1. Refactoring:
Improving the Design
of Existing Code 2nd
Edition
Chapter 6: A first Set of
Refactorings
Chapter 7: Encapsulation
28 July 2022
Efekan AYDEMIR
İ2i Systems Intern

2. Chapter 6: A First
Set of Refactorings
- Extract Function
- Inline Function
- Extract Variable
- Inline Variable
- Change Function Declaration
- Encapsulate Variable

3. A Good Refactoring Cycle

4. Extract Function
- Our aim is putting repeatedly used codes into a function.
- Name it with its job.
- Even it is a single line function you better extract it into function.
- But code only used once should be left inline.

5. Inline Function
- Sometimes, we do
come across a function
in which the body is as
clear as the name
- In such situations,
there is no need to
extract the code.

6. Extract Variable
- It means add a name to
an expression in my code.
- When it comes to
debugging, it will be
easier to investigate.

7. Inline Variable
Variables provide names for
expressions within a function, and
as such they are usually a Good
Thing.
But sometimes, the name doesn’t
really communicate more than the
expression itself.

8. Change Function Declaration

10. Encapsulate Variables
- If we move data around, we have to
change all the references so te data in
a single cycle to keep the coeee
working
- As the scope grows, so does the
difficulty, which is why global data is
such a pain.

11. INTRODUCE PARAMETER OBJECT
Your methods contain a repeating
group of parameters.
Replace these parameters with
an object.

12. Combine Functions Into Transform
Use a data transformation function that
takes the source data as input and
calculates all the derivations, putting each
derived value as a field in the output data.
- Then, to examine the derivations, all I
need do is look at the transform function.

13. Split Phase
-In a split phase refactoring,
we split a tangled piece of
code that does more than one
thing into distinguished
phases that only do a single
thing.
- As a result, we can more
easily and independently
change each of the resulting
phases.

14. Chapter 7:
Encapsulation
- Encapsulate Record
- Encapsulate Collection
- Replace Primitive with Object
- Replace Temp with Query
- Extract Class
- Inline Class
- Hide Delegate
- Remove Middle Man
- Substitute Algorithm

15. Encapsulate Record (Class)
- Create record (class) from object
- Hide what's stored and provide
methods to get value.
- Makes it easier for refactoring
- People can change variables
directly

16. Encapsulate Collection
A class contains a collection field
and a simple getter and setter for
working with the collection.
- Make the getter-returned value read-
only and create methods for
adding/deleting elements of the
collection.

17. Replace Primitive with Object
- A class (or group of classes) contains a data field. The field
has its own behavior and associated data.
- Create a new class, place the old field and its behavior in the
class, and store the object of the class in the original class.

18. Replace Temp with Query
- You place the result of an expression in
a local variable for later use in your code.
- Move the entire expression
to a separate method and
return the result from it.

19. Extract Class
- When one class does the work
of two, awkwardness results.
- Instead, create a new class and place
the fields and methods responsible for
the relevant functionality in it.

20. Inline Class
- A class does almost nothing and isn’t responsible for
anything, and no additional responsibilities are
planned for it.
- Move all features from the class to another one.

21. Hide Delegate
- Calling another object through a delegate.

22. Remove Middle Man

23. Substitute Function
So you want to replace an existing
algorithm with a new one?
Replace the body of the method that
implements the algorithm with a new
algorithm.

25. References
• https://refactoring.guru/
• The Book, Refactoring: Improving the Design of Existing Code by
Martin Fowler
• https://github.com/ittus/Refactoring-summary-2nd-javascript

26. THANKS FOR LİSTENİNG
Contact me : Aydemir081@gmail.com