Refactoring

Question 1

What are the 3 most important steps for refactoring?

Answer 1

At the most abstract level, you’re looking for three things: complexity to break up, duplication to combine, and abstractions waiting to be born

Question 2

What is code smell?

Answer 2

Code smells are warning signs about potential problems in code.

Question 3

What is refactoring?

Answer 3

It’s changing code, without changing business logic in order to improve readability and the ability to update code easier.

Question 4

When we should avoid doing refactoring?

Answer 4

• Project almost finished
• This place won’t be changed in the future
• Renaming of the open interface ( public API ) - Be careful

Question 5

What is Extract Method technique?

Answer 5

Allows us to translate code in method and this method explains the purpose of the code.

We have:

puts ‘Something’
puts ‘Something 2’
puts ‘Something 3 ‘

We translate to:

def print_details
  puts 'Something'
  puts 'Something 2'
  puts 'Something 3 '
end

Question 6

What is Inline method technique?

Answer 6

When the method’s body is straightforward and you don’t need to explain it via method then you can remove this method.

We have:
def more_than_five(number)
number > 5
end

We translate to:

number > 5

Question 7

What is Inline Temp variable technique?

Answer 7

We can remove the variable if we use it only once.

We have:

price = Sample.price
return price > 0

We translate to:

return Sample.price > 0

Question 8

What is Replace Temp Variable with Query technique?

Answer 8

When we replace variable with a method.

We have:

price = one_value * second_value
return price > 0

We translate to:

def price
one_value * second_value
end

return price > 0

Question 9

What is Introduce Explaining variable technique?

Answer 9

When we moving the difficult part under the variable

We have

def hello(a, b)
b2 + (2ab)
end

We translate to

def hello(a, b)
  calculation1 = b**2
  calculation2 = (2*a*b)

calculation1 + calculation2
end

Question 10

What is Replace Method with Method object?

Answer 10

When we replace the long method (many params) with a class

We have

def calculate(price, amount)
  do_something(price, amount)
  do_something_else(price, amount)
end

We translate to

class Calculate
  def initialize(price, amount)
    @price = price
    @amount = amount
  end

  def call
    do_something
    do_something_else
  end

  def do_something
  end

def do_something_else
end
end

def calculate(price, amount)
Calculate.new(price, amount).call
end

Question 11

What is Move field and Move method technique?

Answer 11

When other class uses this method/field more often than yours.

Question 12

What is Inline class technique?

Answer 12

When a class does almost nothing we can move his functional to another class and remove it

Question 13

What is Extract class technique?

Answer 13

When your class does too much work which you can split it between several classes.

Question 14

What is Remove middle man technique?

Answer 14

When a class does too much delegation works we can remove this delegation and use real methods.

Question 15

What is Introduce local extension technique?

Answer 15

When you want to extend class with a new method but class is not available for modification, you can create a copy of this class with inheritance and add this method there.

Question 16

What is replace data value with object technique?

Answer 16

When you use simple data but it isn’t enough and you can create an object to handle it ( For example Money instead of number)

Question 17

What is replace type code with subclass technique?

Answer 17

When your class has many types with different (if/else) logic you can create a subclass for each of these types and move this logic there.

Question 18

What is replace conditional operator with polymorphism?

Answer 18

When you have a method with many switch/if conditions then you can create a subclass for each of these methods and move this logic there.