Learning ruby part 1 conditionals, good and bad code

16 Sep Learning ruby part 1 conditionals, good and bad code

Posted at 15:15h in Ruby by
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In the next code we’ll see:

  • Using conditionals in ruby: If, Else, unless and when we should use one or other one
  • How to evaluate a nill condition
  • Sort circuit assignment (conditional in one line)

The good code and the bad code

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if !tweets.empty?
  puts “timeline”
  puts tweets
end

is better the next code

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unless tweets.empty?
  puts “timeline”
  puts Tweets
end

but when we need to use and else condition is bad to use the unless and is better use the if

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if tweets.empty?
  puts “you dont have tweets”
else
  pust tweets
end

At the moment to use the nil

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if result_proces != nil
   puts “good result”
end

The correct way is only

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if result_process
  puts “good job”
end

More conditionals for example if you want to evaluated some string the correct way can be

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if string.length
   Do something
end

inline conditionals

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if password.lenght < 8
   pust “The password is short”
end

In one line the conditional looks like:

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puts “The password is short” if password.lenght < 8
puts “fail” unless username

More conditionals we can see the next

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if user
if user.signed_in?
#Some logic here
end
 end

We can write better the next

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if user && user.signed_in?
##
 end

Short circuit assigment

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result = nil  || 1  #this will return 1
result = 1  || nil   #this will return 1
result = 1  || 2  #this will return 1

More examples sort circuit

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def sign_in
current_session || sign_user_in
 end

Conditional assigments

the next is a conditional assigment to asign one value to a variable, we can observe in the second line that if the var is nil o empty we assign and value 2:

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i_was_set = 1
i_was_set || = 2
puts i_was_set #print 1

For example in the next example if we are not assigne some value before at do the conditional then this will ocurr

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i_was_no_set || = 3
puts i_was_not_set #print 3

New example for assigments

we have the next code

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options[:country] = ‘us’ if options[:country].nil?
options[:privacy] = true if options[:privacy].nil?
options[:geotag] = true if options[:geotag].nil?

We can refactor with the next code:

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options[:country] || = ‘us’
options[:privacy] || = true
options[:geotag] || = true

Conditionals return values, we can the next code:

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if list_name
  options[:path] = ‘/#{user_name} / #{last_name}’
else
  options[:path] = ‘#{user_name}’
end

We can refactor the before code with the next one:

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options[:path]= if list_name
 ‘/#{user_name} /#{last_name}’
else
 ‘#{user_name}’
end

Because by default ruby return a value for example in one function

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def list_name
 if list_name
  ‘/#{user_name} / #{last_name}’
 else
  ‘#{user_name}’
 end
end

And now lets go to do some exercise to practice a little:

Unless
We’re putting together a system to manage our vast video game collection that we just can’t seem to part with. Using ifwith negative conditions can be tough to read. Refactor the code below to use unless rather than if.

Origin code

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games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
 if !games.empty?
   puts "Games in your vast collection: #{games.count}"
 end

Result code

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games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
unless games.empty?
  puts "Games in your vast collection: #{games.count}"
end

Inline Statements
Doing a full unless statement is sometimes too much. Refactor the method below to use a single-line unless statement.

Origin code

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games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
unless games.empty?
  puts "Games in your vast collection: #{games.count}"
end

Result Code

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games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
puts "Games in your vast collection: #{games.count}" unless games.empty?

Let’s implement a simple search feature – for our naive implementation, we search for a game by its exact title, and if it’s found, we show it. Comparing something with nil in an if statement isn’t needed in Ruby. Refactor the code below to run without the nil comparison.

Origin code

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search = "Contra"
games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
search_index = games.find_index(search)
if search_index != nil
  puts "Game #{search} Found: #{games[search_index]} at index #{search_index}."
else
  puts "Game #{search} not found."
end

Result code

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search = "Contra"
games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
search_index = games.find_index(search)
if search_index
  puts "Game #{search} Found: #{games[search_index]} at index #{search_index}."
else
  puts "Game #{search} not found."
end

Let’s clean up our code to make it search within each game title and show all the results. If it’s an exact match, we’ll show something special. Clean up the code below to short circuit the if statement.

Origin code

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search = "Super Mario Bros."
 games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
 matched_games = games.grep(Regexp.new(search))
 
# Found an exact match
 if matched_games.length > 0
if matched_games.include?(search)
puts "Game #{search} found."
end
 end

Result Code

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search = "Super Mario Bros."
 games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
 matched_games = games.grep(Regexp.new(search))
 
# Found an exact match
 if matched_games.length > 0 && matched_games.include?(search)
puts "Game #{search} found."
 end

If no search is entered, we’ll display all games. Notice the first line below where we’re setting search to an empty string? Change this to use conditional assignment.

Origin code

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search = "" unless search
 games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
 matched_games = games.grep(Regexp.new(search))
 puts "Found the following games..."
 matched_games.each do |game|
puts "- #{game}"
 end

Result code

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search ||= ""
games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
matched_games = games.grep(Regexp.new(search))
puts "Found the following games..."
matched_games.each do |game|
puts "- #{game}"
end

Clean up the code below to only set search_result once by using a conditional return on the if statement.

Origin code

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search = "Contra"
 games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
 search_index = games.find_index(search)
 if search_index
search_result = "Game #{search} found: #{games[search_index]} at index #{search_index}."
 else
search_result = "Game #{search} not found."
 end
 puts search_result

Result Code

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search = "Contra"
 games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
 search_index = games.find_index(search)
 search_result= if search_index
"Game #{search} found: #{games[search_index]} at index #{search_index}."
 else
"Game #{search} not found."
 end
 puts search_result

One of the most common places to use conditional returns is within methods. Refactor the code below, removing the search_result variable all together.

Origin code

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def search(games, search_term)
 search_index = games.find_index(search_term)
 search_result = if search_index
"Game #{search_term} found: #{games[search_index]} at index #{search_index}."
 else
"Game #{search_term} not found."
 end
 return search_result
 end
 
games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
 puts search(games, "Contra")

Result code

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def search(games, search_term)
 search_index = games.find_index(search_term)
 if search_index
  "Game #{search_term} found: #{games[search_index]} at index #{search_index}."
 else
  "Game #{search_term} not found."
 end
end
 
games = ["Super Mario Bros.", "Contra", "Metroid", "Mega Man 2"]
puts search(games, "Contra")

Using Short-Circuit Evaluation can clean up your code a great deal. Update the following method to use short circuit evaluation. While you’re at it, why not try reducing the entire method to one line?

origin code

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def search_index(games, search_term)
 search_index = games.find_index(search_term)
 if search_index
  search_index
 else
  "Not Found"
 end
end

Result code

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def search_index(games, search_term)
  search_index = games.find_index(search_term) || "Not Found"
end


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