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Booleans¶

Booleans are used to represent true or false values. In Ruby the true and false are each individual classes. The class for true is TrueClass and the false is FalseClass.

Creating Booleans¶

Check the class for true and false as follows :

irb(main):001:0> true.class
=> TrueClass
irb(main):002:0> false.class
=> FalseClass

Expression Trees¶

Booleans are used in evaluation expressions.

>> n = 20
=> 20
>> n >= 20
=> true

Additional expression tests :

>> name = "Joseph"
=> "Joseph"
>> name == "Prudence" && n > 20
=> false

if statement¶

We can also use the if statement to check for a true of false condition. The if statement have the following syntax :

if <boolean express>
 #statements here
end

for example :

if company == "Peruzal"
    puts "Company is #{company}"
end

Negation¶

The ! negates the boolean statement :

x = false
if !x
 puts "x is false"
end

Multiple tests¶

We can perform multiple logical operations. The result should be boolean :

ruby = "nifty"
programming = "fun"

if ruby == "nifty" && programming == "fun" # using the and operator
 puts "Keep programming!"
end

if ruby=="nifty" and programming=="fun" and weather=="nice" # using the and logical operator
  puts "Stop programming and go outside!"
end

if a == 10 || b == 27 || c = 43 || d = −14 # using the ||(or) logical operator
 print sum = a + b + c + d
end

if ruby == "nifty" or programming == "fun" # using the or logical operator
 puts "Keep programming!"
end

Putting `if` at the end of the statement¶

For one line if statements, you can place the if condition at the end of the statement as follows :

puts "Ruby is great" if true

The `else` statement¶

Add an optional else to execute a statement when if is not true:

if x >= y
 puts "x greater than or equal to y"
else
 puts "x is not greater than or equal to y"
end

The `elsif` statement¶

Use one or more optional elsif statements to test multiple statements (ending with an optional else, which must be last):

if x == y
 puts "x equals y"
elsif x != y
 puts "x is not equal to y"
elsif x > y
 puts "x is greater than y"
elsif x < y
 puts "x is less than y"
else
 puts "Well, i dont what is x and y is"
end

`unless` statement¶

The unless statement is the negation of an if statement.

unless company == "Peruzal"
 company = "Unknown"
else
 company = "Peruzal"
end

The equivalent if statement :

if company == "Peruzal"
 company = "Peruzal"
else
 company = "Unknown"
end

Shot unless statement¶

We can also add the unless at the end of the statement as follows :

company = ""
puts "I don't know your company" unless company == "Peruzal"

Tenary operator¶

For short if else expression and then assign a variable, we can use the tenary operator ?: as follows :

>> (company.eql?"Peruzal") ? "Yes" : "No"
=> "Yes"

We usually assign the value returned to a variable. The ternary operator is a shortened version of the if-else construct.