Ruby Language Ruby Access Modifiers Instance Variables and Class Variables
Example
Let's first brush up with what are the Instance Variables: They behave more like properties for an object. They are initialized on an object creation. Instance variables are accessible through instance methods. Per Object has per instance variables. Instance Variables are not shared between objects.
Sequence class has @from, @to and @by as the instance variables.
class Sequence
include Enumerable
def initialize(from, to, by)
@from = from
@to = to
@by = by
end
def each
x = @from
while x < @to
yield x
x = x + @by
end
end
def *(factor)
Sequence.new(@from*factor, @to*factor, @by*factor)
end
def +(offset)
Sequence.new(@from+offset, @to+offset, @by+offset)
end
end
object = Sequence.new(1,10,2)
object.each do |x|
puts x
end
Output:
1
3
5
7
9
object1 = Sequence.new(1,10,3)
object1.each do |x|
puts x
end
Output:
1
4
7
Class Variables Treat class variable same as static variables of java, which are shared among the various objects of that class. Class Variables are stored in heap memory.
class Sequence
include Enumerable
@@count = 0
def initialize(from, to, by)
@from = from
@to = to
@by = by
@@count = @@count + 1
end
def each
x = @from
while x < @to
yield x
x = x + @by
end
end
def *(factor)
Sequence.new(@from*factor, @to*factor, @by*factor)
end
def +(offset)
Sequence.new(@from+offset, @to+offset, @by+offset)
end
def getCount
@@count
end
end
object = Sequence.new(1,10,2)
object.each do |x|
puts x
end
Output:
1
3
5
7
9
object1 = Sequence.new(1,10,3)
object1.each do |x|
puts x
end
Output:
1
4
7
puts object1.getCount
Output: 2
Shared among object and object1.
Comparing the instance and class variables of Ruby against Java:
Class Sequence{
int from, to, by;
Sequence(from, to, by){// constructor method of Java is equivalent to initialize method of ruby
this.from = from;// this.from of java is equivalent to @from indicating currentObject.from
this.to = to;
this.by = by;
}
public void each(){
int x = this.from;//objects attributes are accessible in the context of the object.
while x > this.to
x = x + this.by
}
}
