Defining Class Constants in JRuby
In this example you will learn about using Class
Constants in JRuby program. Constants can be defined within the scope of
classes, but they are not as instance variables, constants can be accessed
from outside the class. Constants have name starting with the upper case letter.
In this example we have created a class and this class
consists of three class constants Constant1, Constant2, Constant3 and we
have initialized them with integer values 10, 20, 30 respectively. printAll
method of class ConstantClass will print all constants values since they
are accessible within class.
"puts Constant1" outside the class
will report an error because it can be accessed outside the class with the class
name as given below:
| "ConstantClass::Constant1" |
Here is the example code of ConstantsJRuby.rb as
follows:
ConstantsJRuby.rb
# Class constants Example
class ConstantClass
Constant1 = 10
Constant2 = 20
Constant3 = 30
def printAll
puts "Value of first constant =
#{Constant1}"
puts "Value of first constant =
#{Constant2}"
puts "Value of first constant =
#{Constant3}"
end
end
const = ConstantClass.new
puts const.printAll
# puts Constant1 will invoke NameError
# uninitialized constant Constant1
puts "Constant Value ==> #{ConstantClass::Constant1}"
puts "Constant Value ==> #{ConstantClass::Constant2}"
puts "Constant Value ==> #{ConstantClass::Constant3}" |
Output:
After executing ConstantsJRuby.rb on command
prompt with jruby command, you will get the following output:
C:\JRuby>jruby ConstantsJRuby.rb
Value of first constant = 10
Value of first constant = 20
Value of first constant = 30
nil
Constant Value ==> 10
Constant Value ==> 20
Constant Value ==> 30 |
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