Code Smells

Question 1

Why shouldn’t you use ‘Comments’? ( 3 points )

Answer 1

• Communication.
  It’s hard to understand and read the code if comments have another meaning than a method
• Flexibility.
  It’s hard to support and change( Every time when you update the code you should also update the comment )
• Duplication.
  You don’t need to write the same comment if your method name has already explained it.

Question 2

When can we use ‘Comments’? ( 3 points )

Answer 2

• Explain difficult algorithm
• For some automation tolls ( annotate for example )
• To get the link to the guide which explains core behavior

Question 3

Why shouldn’t we use ‘Long methods’? ( 2 )

Answer 3

• Flexibility
  The long method contains too many responsibilities, that’s why it won’t be flexible for change.
• Testability
  It may be difficult to set up all initial behavior and test it.

Question 4

Why shouldn’t we use ‘Long class/modules? ( 2 )

Answer 4

• Flexibility
  Too many responsibilities and hard to change
• Testability
  Hard to test. We need to create too many setups before tests running.

Question 5

Why shouldn’t we use ‘Long parameter list’?

Answer 5

• Simplicity
  It tells us that the method tries to do too much and we should try to group params as an object together.
• Flexibility
  If we add new params, we need to update all invoke of the method. It’s not flexible
• Communication
  You should remember lot’s of things

Question 6

What is ‘embedded in name’ smell?

Answer 6

When you add unnecessary value to the name:
- add_course(course)
When you add type to the name
- animal_string

Question 7

What is ‘uncommunicative name’ smell?

Answer 7

When you use:
- One or two-character names
- Misleading names
- abbreviations

Question 8

What is ‘Inconsistent name’ smell?

Answer 8

One name is used in one place, and a different name is used for the same thing somewhere else. For example, in a single application you might see add, store, put, and place for the same basic method.

Sample: ‘Destroy, delete, remove for the same method;’

Question 9

What is ‘Dead code’ smell?

Answer 9

A variable, parameter, code fragment, method, module, or class is not used anywhere (perhaps other than in tests).

Question 10

Why should we remove ‘Dead code’?

Answer 10

• Size( adds to the application’s size, and thus to the amount of code that must be understood by developers and maintainers)
• Communication ( hard to understand intentions)
• Flexibility (It’s stupid to support unused code)

Question 11

What is ‘Speculative generality’ code smell?

Answer 11

The same as You ain’t gonna need it

This code smell describes a situation where people develop a class with all sorts of hooks and special cases just so it will handle things that might be required in the future but not at this stage

Question 12

What is ‘Greedy Method’ code smell?

Answer 12

When code do more than one job or have several levels of abstraction. ( More than one responsibility )

Question 13

What is ‘Procedural code’ smell?

Answer 13

Don’t use procedural code ( like loop, while with temp variables) if you can use each

Question 14

What is ‘Dynamic code creation’ code smell?

Answer 14

Don’t use eval

Question 15

What is Derived Value code smell?

Answer 15

When you have code which was defined from scratch instead of getting from another value:

NAME = ‘Nic’
SURNAME = ‘Mil’
FULL_NAME = ‘Nic Mil’

But we can leave this code smell for the tests.

Question 16

What is Repeated Value code smell?

Answer 16

When you have a string more than one time in the code.
You need to move this string to the constant.

Question 17

What is Duplication code code smell?

Answer 17

Two fragments of code look nearly identical.

Question 18

What is Alternative Modules with Different Interfaces code smell?

Answer 18

Two classes or modules seem to be doing the same thing but are using different method names.

Question 19

What is ‘Nil check` smell?

Answer 19

Try to avoid using nil check

Question 20

What is Special case code smell?

Answer 20

• Complex if statements.
• Guard clauses—checks for particular values before doing work (especially comparisons to constants).

Question 21

What is Complicated Boolean Expression code smell?

Answer 21

Code has complex conditions involving and, or, and not.

Example:
- if !a
- !(a && b)

Question 22

What is Control Coupling code smell?

Answer 22

• A method or block checks the value of a parameter in order to decide which execution path to take.

• A method’s name includes a word such as “or.”

Question 23

What is Simulated Polymorphism code smell?

Answer 23

• Code uses a case statement (especially on a type field).
• Code has several if statements in a row (especially if they’re comparing against the same value).

Question 24

What is ‘Primitive Obsession’ code smell?

Answer 24

(Одержимость примитивными типами)

When you use primitive types as a string on number instead of creating new Class. ( For example Money, Data.. constant that includes Number instead of meaning )

Question 25

What is ‘Data class` code smell?

Answer 25

It’s when a class contains only data ( attr_reader and initializer) but the whole class should contain data and behavior. So, in this case, will be better to use Struct.

Question 26

What is ‘Data clump` code smell?

Answer 26

(Глыба данных) It’s when you tried to send two or more items together in the params list.

Something like cord(x, y, z)
Or something(period_start, period_end, period_middle)

So, you basically need to move these params to the object.

Question 27

What is Temporary Field code smell?

Answer 27

An instance variable is set only in certain circumstances.

class Animal
attr_accessor :type

def show
if type.nil?
p ‘Not Set’
else
p type
end
end

end

animal = Animal.new
animal.type = ‘King’
animal.show

Question 28

What is implemetation inheritance code smell?

Answer 28

So when you use inheritance instead of composition.
Inheritance needs to use for is-a relations and composition for has-a relations.

Instances of the subclass should have the ability to passed as substitutes for instances of the parent.( we can replace parent object with a child object)

Question 29

What is ‘Refused bequest` code smell?

Answer 29

( Отказано в наследстве)

• Explicit Refusal: The subclass undefines an inherited method, makes an inherited method private, or makes it throw an exception when it is called.
• Implicit Refusal: A method inherited from the parent class just doesn’t work for instances of the subclass.

Question 30

What is Inappropriate Intimacy (Subclass form) code smell?

Answer 30

(Неуместная близость)

A class makes use of the implementation details of its superclass.

Question 31

What is Lazy Class code smell?

Answer 31

A class isn’t doing much—its parents, children, or clients seem to be doing all the associated work—and there isn’t enough behavior left in the class to justify its continued existence.

En example -> CreateForm < CoreForm without any behavior, so we shouldn’t create this form for future changes.

Question 32

What is Feature Envy code smell?

Answer 32

(Завистливая функция) A code fragment references another object more often than it references itself.

Example:

class Parcel
def addressee
“#{@person.first_name} #{@person.last_name}”
end
end

Should go to:

class Parcel
def addressee
@person.full_name
end
end

class Person
def full_name
“#{first_name} #{last_name}”
end
end

Question 33

What is Utility Function code smell?

Answer 33

(Функция полезности) - An instance method has no dependency on the state of the instance.

Question 34

What is Global variable code smell?

Answer 34

Your code uses a global variable, other than one predefined by Ruby itself.

Question 35

What is Method Chain code smell?

Answer 35

You see calls of the form a.b.c.d.

This code breaks the Law of Demeter

Question 36

What is Middle Man code smell?

Answer 36

A class that mostly delegates its work is known as a Middle Man:
• Most methods of a class call the same or a similar method on another object:

def f
@delegate.f
end

Question 37

What is Greedy Module code smell?

Answer 37

A module has more than one responsibility—for example, formatting a report as XML and sending it to a SOAP service.

Question 38

What is ‘Divergent change’ code smell?

Answer 38

It’s like Single Responsibility. When the class has many reason to be changed.
For example when the class has ‘send_email’ and ‘update’ method together.
It is likely that changes will be made to different parts of the class for different reasons.