Examples of how to make if else clauses in Ruby nicer and avoid rubocop errors like

Favor modifier if usage when having a single-line body. Another good alternative is the usage of control flow &&/||.

Use self-assignment shorthand +=.

Use a guard clause instead of wrapping the code inside a conditional expression.

More information about making Ruby code looks nicer can be found in the RuboCop docu (Link)

ConditionalAssignment

Rubocop Error:

Style/ConditionalAssignment: Use the return of the conditional for variable assignment and comparison

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# save return value to variable
puts 'save return value to variable'
x = 1

# Bad :-(
if x <= 1
  response = true
else
  response = false
end
puts response

# Good :-)
puts false unless x <= 1
# or
puts true if x <= 1

output:

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$# rspec test.rb
save return value to variable
true
true

IfUnlessModifier

Rubocop Error:

Style/IfUnlessModifier: Favor modifier if usage when having a single-line body. Another good alternative is the usage of control flow &&/||.

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# String comparison
puts 'String comparison'
header = 'HEAD'
head = 'HEAD'

# Bad :-(
if header == head
  puts true
end

# Good :-)
puts true if header.eql? head
# or
puts false unless header.eql? head

output:

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$# rspec test.rb
String comparison
true
true

SelfAssignment

Rubocop Error:

Style/SelfAssignment: Use self-assignment shorthand +=.

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puts 'easy calculation'
i = 1

# Bad :-(
i = 1
i = i + 1
puts i

# Good :-)
i = 1
i += 1
puts i

output:

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$# rspec test.rb
easy calculation
2
2

GuardClause

Rubocop Error:

Style/GuardClause: Use a guard clause instead of wrapping the code inside a conditional expression

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# Bad :-(
puts 'def my_method'
def my_method
  i = 5
  if i > 0
    puts 'i greater 0'
  end
end

# Good :-)
def my_method
  i = 5
  puts 'i greater 0' unless i <0
end

output:

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$# rspec test.rb
def my_method
i greater 0
i greater 0

More complex example

Here is a more complex example:

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# Calculate errors
puts 'calculate errors'
i = 0
exit_code = 0
exist = true
response_code = 2
ii = 5

# Bad :-(
if exist == true
  while i < ii
    if response_code == 2
      exit_code = exit_code + 1
    end
    i = i + 1
  end
end
if exit_code < 0
  puts false
else
  puts true
end

# Good :-)
if exist.eql? true
  while i < ii
    exit_code += 1 unless response_code.eql? 0
    i += 1
  end
end
puts true unless exit_code > 0
# or
puts true if exit_code.eql? 0
# or
puts false unless exit_code.eql? 0

output:

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$# rspec test.rb
calculate errors
true
false

As you can see, you can massively reduce your code.(Source Code)