Multiple constructors?

Hi,

Is it possible to use multiple constructors in Ruby?

class SQLServerConnection

def initialize(server_name, db)

end

def initialize(server_name, db, user_name, password)

end
end

Thank You

Aidy

On Wed, Jul 23, 2008 at 12:09 PM, aidy [email protected]
wrote:

def initialize(server_name, db, user_name, password)

end
end

You can send your initialize an array or hash, or you can do

class C
def initialize( a, b, *c )
#verify and do stuff
end
end

hth,
Todd

On Wed, Jul 23, 2008 at 7:09 PM, aidy [email protected] wrote:

def initialize(server_name, db, user_name, password)

end
end

Thank You

Aidy

First of all initialize is not a constructor but an initializer,
behind the scenes the following happenes

class Object
def self.new *args, &blk
o = allocate
o.send :initialize, *args, &blk # this because #initialize is
always private
o
end
end

As you can see #initialize is an instance method and #new is a
singleton (or class) method.

Secondly, and that holds for all methods, #initialize is only an
example, you cannot “overload” method definitions but simulate that
behavior, in your case I would do the following

class SQLServerConnection

private

def initialize *args
case args.size
when 2
init_name_db *args
when 4
init_user_pw *args
else
error
end
end

def init_name_db server_name, db

end

def init_user_pwd server_name, db, user, pwd

end
end

HTH
Robert


http://ruby-smalltalk.blogspot.com/

There’s no one thing that’s true. It’s all true.

On Jul 23, 2008, at 1:09 PM, aidy wrote:

def initialize(server_name, db, user_name, password)

end
end

Thank You

Aidy

No, but you can have optional parameters by giving a default value or
taking a hash.

def initialize(server_name, db, user_name=nil, password=nil)
if user_name && password
# connect with credentials
else
# connect anonymously
end
end

Called like: SQLServerConnection.new(“myserver”, “development”,
‘aidy’, ‘shh_secret’)

-or-

def initialize(server_name, db, options={})
if options.has_key?(:user) && options.has_key?(:password)
# connect with credentials
else
# connect anonymously
end
end

and called like: SQLServerConnection.new(“myserver”,
“development”, :user => ‘aidy’, :password => ‘shh_secret’)

-Rob

Rob B. http://agileconsultingllc.com
[email protected]

aidy wrote:

Is it possible to use multiple constructors in Ruby?

No.

class SQLServerConnection
def initialize(server_name, db)

end
def initialize(server_name, db, user_name, password)

end
end

def initialize(server_name, db, user_name=nil, password=nil)

end

HTH,
Sebastian

I prefer to use different names for “different constructors”.
Most of the time, I feel that overloading can complicate things,
more-so in a dynamic language.

Just make them class methods:

Foo.from_x()
Foo.with_size()

Etc, etc.

HTH,
Paul

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs