Control Flow: if, elsif, else, unless...

control_flow.rb

# if/elsif/else: 

if expression
  # Do something. Otherwise do nothing and got to next section of code.
end

if expression
  # Do something
else
  # Do yet another thing. Default response.
end

if expression
  # Do something
elsif expression
  # Do something else
else
  # Do yet another thing. Default response.
end

##################################################################################################

# unless:
# Sometimes you want to use control flow to check if something is false, rather than if it's true.
# Ruby will let you use an unless statement.
# Basically a short hand if statement. It will do whatever you ask unless the condition is true. 

# unless syntax looks like this:

unless condition
  # Do something!
end

# For unless, the "# Do something!" bit will execute if the condition evaluates to false.


hungry = false

unless hungry # Looks to see if expression is false.
  puts "I'm writing Ruby programs!" # It does this if false.
else
  puts "Time to eat!" # It does this if true.
end

#=> "I'm writing Ruby programs!"


power_on = true

unless power_on
	puts "Start the car."
else 
	puts "Turn off the car."
end

#=> "Turn off the car."

problem = false
print "Good to go!" unless problem
#=> "Good to go!"