Wrong results using named arguments

ruby-talk
1

Source:

[a.rb]
class A

  attr_accessor :id
  attr_accessor :name

  def initialize(id = nil, name = nil)
    @id = id
    @name = name
  end
end

[test.rb]
require 'a'

a1 = A.new(:name => "test")
a2 = A.new(:name => "test2")

p a1
p a2

Results:
#<A:0x28c2d80 @id={:name=>"test"}, @name=nil>
#<A:0x28c2678 @id={:name=>"test2"}, @name=nil>

I expected:

#<A:0x28c2d80 @id=nil, @name="test">
#<A:0x28c2678 @id=nil, @name="test2">

So what nuby mistake am I making?

Thanks,
Jason

2

Ruby really doesn't have named arguments, rather it uses a hash to fake it.

Your initialize method for A should probably be written
     def initialize(args)
               @id = args[:id]
               @name = args[:name]
       end

Farrel

···

On 29/11/06, Jason Vogel <jasonvogel@gmail.com> wrote:

Source:

[a.rb]
class A

        attr_accessor :id
        attr_accessor :name

        def initialize(id = nil, name = nil)
                @id = id
                @name = name
        end
end

[test.rb]
require 'a'

a1 = A.new(:name => "test")
a2 = A.new(:name => "test2")

p a1
p a2

Results:
#<A:0x28c2d80 @id={:name=>"test"}, @name=nil>
#<A:0x28c2678 @id={:name=>"test2"}, @name=nil>

I expected:

#<A:0x28c2d80 @id=nil, @name="test">
#<A:0x28c2678 @id=nil, @name="test2">

So what nuby mistake am I making?

Thanks,
Jason

3

Jason Vogel wrote:

Source:

[a.rb]
class A

attr_accessor :id
attr_accessor :name

def initialize(id = nil, name = nil)
@id = id
@name = name
end
end

[test.rb]
require 'a'

a1 = A.new(:name => "test")
a2 = A.new(:name => "test2")

As your class is written, you must provide values:

a1 = A.new("id","test")

Do you want to define a hash with key-value pairs? Do it this way:

def initialize(key,value)
  @hash = {}
  @hash[key] = value
end

In a post like this, always say explicitly what you want to accomplish.

···

--
Paul Lutus
http://www.arachnoid.com

4

Jason Vogel:

class A

  attr_accessor :id
  attr_accessor :name

  def initialize(id = nil, name = nil)
    @id = id
    @name = name
  end
end

# [...]

require 'a'

a1 = A.new(:name => "test")
a2 = A.new(:name => "test2")

p a1
p a2

Results:
#<A:0x28c2d80 @id={:name=>"test"}, @name=nil>
#<A:0x28c2678 @id={:name=>"test2"}, @name=nil>

Your initialize method takes two (optional) arguments, the first of which
is id. In your calls to A.new, you're passing exactly one argument, which
is why id gets set, and name does not. More precisely,

  A.new(:name => 'test')

is the same as

  A.new({:name => 'test'})

so you're passing a Hash. To achieve what you may want, do

  def initialize(opt = {})
    @id = opt[:id]
    @name = opt[:name]
  end

Kalman