It comes up very often. Should I use alias or alias_method . Let’s take a look at them in a bit detail.
Usage of alias
class User
def full_name
puts "Johnnie Walker"
end
alias name full_name
end
User.new.name #=>Johnnie Walker
Usage of alias_method
class User
def full_name
puts "Johnnie Walker"
end
alias_method :name, :full_name
end
User.new.name #=>Johnnie Walker
First difference you will notice is that in case of alias_method
we need to use a comma between the “new method name” and “old method name”.
alias_method
takes both symbols and strings as input. Following code would also work.
alias_method 'name', 'full_name'
That was easy. Now let’s take a look at how scoping impacts usage of alias
and alias_method
.
Scoping with alias
class User
def full_name
puts "Johnnie Walker"
end
def self.add_rename
alias_method :name, :full_name
end
end
class Developer < User
def full_name
puts "Geeky geek"
end
add_rename
end
Developer.new.name #=> 'Gekky geek'
In the above case method “name” picks the method “full_name” defined in “Developer” class. Now let’s try with alias
.
class User
def full_name
puts "Johnnie Walker"
end
def self.add_rename
alias :name :full_name
end
end
class Developer < User
def full_name
puts "Geeky geek"
end
add_rename
end
Developer.new.name #=> 'Johnnie Walker'
With the usage of alias
the method “name” is not able to pick the method “full_name” defined in Developer.
This is because alias
is a keyword and it is lexically scoped. It means it treats self as the value of self at the time the source code was read. In contrast alias_method
treats self as the value determined at the run time.
Overall my recommendation would be to use alias_method
. Since alias_method
is a method defined in class Module it can be overridden later and it offers more flexibility.
FYI: