Protected and Private methods
- by cabaret
I'm reading through Beginning Ruby and I'm stuck at the part about private and protected methods. This is a newbie question, I know. I searched through SO for a bit but I couldn't manage to find a clear and newbie-friendly explanation of the difference between private and protected methods.
The book gives two examples, the first one for private methods:
class Person
def initialize(name)
set_name(name)
end
def name
@first_name + ' ' + @last_name
end
private
def set_name(name)
first_name, last_name = name.split(/\s+/)
set_first_name(first_name)
set_last_name(last_name)
end
def set_first_name(name)
@first_name = name
end
def set_last_name(name)
@last_name = name
end
end
In this case, if I try
p = Person.new("Fred Bloggs")
p.set_last_name("Smith")
It will tell me that I can't use the set_last_name method, because it's private. All good till there.
However, in the other example, they define an age method as protected and when I do
fred = Person.new(34)
chris = Person.new(25)
puts chris.age_difference_with(fred)
puts chris.age
It gives an error:
:20: protected method 'age' called for #<Person:0x1e5f28 @age=25> (NoMethodError)
I honestly fail to see the difference between the private and protected methods, it sounds the same to me. Could someone provide me with a clear explanation so I'll never get confused about this again?
I'll provide the code for the second example if necessary.
