Defining an object constructor that look like [] or {} ...?


#1

Hey Guys,

Ruby has built in object constuctors for Array and Hash via [] and {}…
ie:

an_array = [1, 2, 3, 6]
a_hash = {1=>3, 2=>5, ‘a’=>‘green’}

I would like to do the same for one of my classes… i.e.

my_object = |2, 3, 5, 7|

should yield the same result as if I had done the following:

my_object = MyClass.new([2, 3, 5, 7])

Is this possible?

Sonny.


#2

my_object = MyClass.new([2, 3, 5, 7])

You should be able to use

[] as class method:

my_object = MyClass[2, 3, 5, 7]

a method in Kernel or similar:

my_object = MyClass(2, 3, 5, 7)

tom.


#3

On Jan 16, 2009, at 1:15 PM, Sonny C. wrote:

my_object = |2, 3, 5, 7|

should yield the same result as if I had done the following:

my_object = MyClass.new([2, 3, 5, 7])

Is this possible?

Offhand, I doubt you can use || for this task, but you can use [].

 class MyClass
   def MyClass.[](*arr)
     MyClass.new(arr)
   end

   def initialize(arr)
     @arr = arr
   end
 end

 > x = MyClass[2, 3, 5, 7]
 => #<MyClass:0x7a3b4 @arr=[2, 3, 5, 7]>

#4

On 16.01.2009 20:15, Sonny C. wrote:

should yield the same result as if I had done the following:

my_object = MyClass.new([2, 3, 5, 7])

Is this possible?

No, because you would have to change Ruby’s syntax. See the other
postings for alternatives.

Kind regards

robert


#5

Le 16 janvier 2009 à 20:26, Tom L. a écrit :

my_object = MyClass(2, 3, 5, 7)

A method in Array :

class Array
def to_my_class
MyClass.new(self)
end
end

my_object = [2, 3, 5, 7].to_my_class

Fred