TechDiscuss.net Shaunak Sontakke
Code Smells & Refactoring
Those Smells
TechDiscuss.net Shaunak Sontakke
Shaunak Sontakke
● Bachelor of Engineering, MBA in Systems
● Software Engineer @ Entrata
● Full Stack Developer for 13 years, HusBand for 6 years and Dad for 4 years
● Passionate about clean architecture, clean code, pragmatic development
● Love reading/listening Self-Help Books, Developer Podcasts
● Blog: TechDiscuss.net. Email: [email protected]
TechDiscuss.net Shaunak Sontakke
Hello Everyones,
Todays are a great day. I is happy because we are learning new thing’s.
TechDiscuss.net Shaunak Sontakke
Code Smells
● Deeper problems
● Not bugs, nor errors
● Possibly
○ Weakness
○ Defects
○ Inefficiency
○ Design principles violation
● Ignore? Sure for cascading failures
● Agile software development term
● Code Smell Catalog gives you vocabulary in code review discussions
● Code Smells vs Anti-Pattern
TechDiscuss.net Shaunak Sontakke
Code Smells Catalog
1. Alternative classes w/ different interfaces
2. Comments
3. Data class
4. Data clumps
5. Dead code
6. Divergent change
7. Duplicated code
8. Feature envy
9. Inappropriate intimacy
10. Incomplete library client
11. Large class
12. Lazy class
13. Long method
14. Long parameter list
15. Message chains
16. Middle man
17. Parallel inheritance hierarchies
18. Primitive obsession
19. Refused bequest
20. Shotgun surgery
21. Speculative generality
22. Switch statements
23. Temporary field
TechDiscuss.net Shaunak Sontakke
Code Smells Catalog
1. Alternative classes w/ different interfaces
2. Comments
3. Data class
4. Data clumps
5. Dead code
6. Divergent change
7. Duplicated code
8. Feature envy
9. Inappropriate intimacy
10. Incomplete library client
11. Large class
12. Lazy class
13. Long method
14. Long parameter list
15. Message chains
16. Middle man
17. Parallel inheritance hierarchies
18. Primitive obsession
19. Refused bequest
20. Shotgun surgery
21. Speculative generality
22. Switch statements
23. Temporary field
TechDiscuss.net Shaunak Sontakke
Code Smells Catalog
1. Long method
2. Large class
3. Data clumps
4. Long parameter list
5. Primitive obsession
1. Alternative classes w/ different interfaces
2. Refused bequest
3. Switch statements
4. Temporary field
1. Divergent change
2. Shotgun surgery
3. Parallel inheritance hierarchies
1. Feature envy
2. Inappropriate intimacy
3. Message chains
4. Middle man
1. Comments
2. Data class
3. Dead code
4. Duplicated code
5. Lazy class
6. Speculative generality
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TechDiscuss.net Shaunak Sontakke
Code Smell Groups
Change Preventers
If you want to change
something in one
place you have to
make many changes in
other places too
Excessive coupling
between classes
Couplers Object-Orientation
Abusers
Incomplete or
incorrect
implementation of
OOP
Bloaters
Grown to a large size
Dispensables
Absence of these
would make the code
clean and improve
code readability
TechDiscuss.net Shaunak Sontakke
Long method
● Ask questions if the method is more than 10 lines
● Probably violating design principles like SRP, KISS
Bloaters
Grown to a large size
TechDiscuss.net Shaunak Sontakke
Long method
Large class
● Class doing too many things
● Too many member variables
● Breeding ground for duplicate code
Bloaters
Grown to a large size
TechDiscuss.net Shaunak Sontakke
Data clumps
Long method
Large class
● Like children - enjoy hanging around in groups
● Same set of variables seen together
● name_first-name_last, start_date-end_date
Bloaters
Grown to a large size
TechDiscuss.net Shaunak Sontakke
Long method
Long parameter list
Large class
Data clumps
● More parameters ~ doing more things
● Another object hiding there
● SonarQube defaults: 4 is good
● Uncle Bob’s Clean Code: More than 3 requires
special justification
function doSomething($param1, $param2, $param3,
$param4, $param5) {
...
}
Bloaters
Grown to a large size
https://rules.sonarsource.com/php/RSPEC-107?search=parameter
TechDiscuss.net Shaunak Sontakke
Long method
Primitive obsession
Long parameter list
Large class
Data clumps
● Developers prefer primitive types like floats for
money / currency classes, 2 string dates vs
DateRange object
● Developers reluctant to use small objects for small
tasks
Bloaters
Grown to a large size
TechDiscuss.net Shaunak Sontakke
Long method
Primitive obsession
Long parameter list
Large class
Data clumps
Bloaters
Grown to a large size
TechDiscuss.net Shaunak Sontakke
Divergent change
● Requires you to change multiple unrelated
methods when you want to do a small change in
class
● Adding a new coupon code functionality? Change
shipping function, printing function, order function,
etc.
● Applicable to changes in one class
Change Preventers
If you want to change
something in one
place you have to
make many changes in
other places too
TechDiscuss.net Shaunak Sontakke
Divergent change
Shotgun surgery
● One reason for changing multiple classes
● Similar to Divergent Change
● Divergent change is many changes to one class,
while shotgun surgery is single change modifying
multiple classes
Change Preventers
If you want to change
something in one
place you have to
make many changes in
other places too
TechDiscuss.net Shaunak Sontakke
Divergent change
Shotgun surgery
Parallel inheritance
hierarchies
Departments
HR Marketing
Privilege
HRPrivileges MarketingPrivileges
Sales SalesPrivele
ges
Change Preventers
If you want to change
something in one
place you have to
make many changes in
other places too
TechDiscuss.net Shaunak Sontakke
Divergent change
Shotgun surgery
Parallel inheritance
hierarchies
Change Preventers
If you want to change
something in one
place you have to
make many changes in
other places too
TechDiscuss.net Shaunak Sontakke
Feature envy
● Method is more interested in a another class
● Accesses more public features of other class than
its own
class SalaryCalculator {
public function calculateTotal() {
$tax = $this->calculateTax();
}
public function calculateTax() {
$employee = new Employee();
$grossTotal = $employee->getTotalPay()
+ $employee->getTotalBonus();
// ...
return $tax;
}
}
Excessive coupling
between classes
Couplers
TechDiscuss.net Shaunak Sontakke
Feature envy
Inappropriate intimacy
● Class touches internal fields and methods of
another class
● Compromises other class's encapsulation
class Customer {
public function sendSms( $name, Contact $contact ) {
$message = 'Hello '. $name;
$message .= 'Contact:' . $contact->getPhoneNumber() .
PHP_EOL;
$message .= 'Email:' . $contact->getEmail() . PHP_EOL;
}
}Excessive coupling
between classes
Couplers
TechDiscuss.net Shaunak Sontakke
● Class that uses another class’s method, which in
turn uses another class’s and so on
● Chain: Employee->EmployeeConfig->Config
Feature envy
Inappropriate intimacy
Message chains
class Employee {
public function getConfiguration() {
$this->employeeConfig->getConfiguration();
}
}
class EmployeeConfig {
public function getConfiguration() {
$this->config->getConfiguration();
}
}
class Config {
public function getConfiguration() {
$this->loadConfiguration();
}
}
Excessive coupling
between classes
Couplers
TechDiscuss.net Shaunak Sontakke
● Class exists just to delegate to another
● Is there a real purpose of this class?Feature envy
Middle man
Inappropriate intimacy
Message chains
class Customer {
/** @var Person */
private $person;
public function getNameFir
