It isn't possible to define a class method [] (to make a constructor)
for a struct is it?
If you have:
Customer = Struct.new( "Customer", :name, :address, :zip )
joe = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )
but you want it to be:
joe = ["Joe Smith", "123 Maple, Anytown NC", 12345]
Ruby will just make joe an array, right? No way around this that I
can see, is there?
Alle giovedì 15 novembre 2007, Wayne Magor ha scritto:
It isn't possible to define a class method (to make a constructor)
for a struct is it?If you have:
Customer = Struct.new( "Customer", :name, :address, :zip )
joe = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )but you want it to be:
joe = ["Joe Smith", "123 Maple, Anytown NC", 12345]
Ruby will just make joe an array, right? No way around this that I
can see, is there?
You can't instruct ruby to create a class different from Array for the [x,
y, ...] construct, but you can define a method for a class, and use it to
create a new istance of the class:
class A
def initialize x, y
@x = x
@y = y
end
def A.(x, y)
new x, y
end
end
a = A[1, 2]
Since your Customer class was created using Struct.new, it already provides
this feature (at least, my trials show this, although I couldn't find
documentation about this). So, you can write:
joe = Customer["Joe Smith", "123 Maple, Anytown NC", 12345 ]
I hope this helps
Stefano
It isn't possible to define a class method (to make a constructor)
for a struct is it?If you have:
Customer = Struct.new( "Customer", :name, :address, :zip )
joe = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )but you want it to be:
joe = ["Joe Smith", "123 Maple, Anytown NC", 12345]
Ruby will just make joe an array, right?
Of course you cannot change the semantics of the array constructor.
No way around this that I
can see, is there?
Of course there is, this is Ruby. 
irb(main):001:0> Test = Struct.new :foo, :bar do
irb(main):002:1* class <<self
irb(main):003:2> alias :initialize :
irb(main):004:2> end
irb(main):005:1> end
=> Test
irb(main):006:0> Test[1,2]
=> #<struct Test foo=1, bar=2>
irb(main):007:0>
Kind regards
robert
2007/11/15, Wayne Magor <Wayne.Magor@gmail.com>:
--
use.inject do |as, often| as.you_can - without end
Stefano Crocco wrote:
this feature (at least, my trials show this, although I couldn't find
documentation about this). So, you can write:joe = Customer["Joe Smith", "123 Maple, Anytown NC", 12345 ]
I also missed the docs for this since I was looking in the old pick-axe
book included with Ruby dists. It's actually documented in the second
edition book on page 627. Thanks.
So how is defined in Ruby? Just curious. It must be a special-case.
--
Posted via http://www.ruby-forum.com/\.
It's just a singleton method on the class object; "" is a valid method name.
joe = Customer.send(:, "Joe Smith", "123 Maple, Anytown NC", 12345)
You can define a # method on anything.
-mental
On Fri, 16 Nov 2007 01:05:44 +0900, Wayne Magor <wemagor2@gmail.com> wrote:
So how is defined in Ruby? Just curious. It must be a special-case.
Wayne Magor wrote:
So how is defined in Ruby? Just curious.
obj[stuff] is syntactig sugar for obj.(stuff) and obj[stuff]=otherstuff is
syntactic sugar for obj.=(stuff,otherstuff). Stuff can be multiple values
seperated by commas, otherstuff can't.
It must be a special-case.
Not more so than <, >, <=, >=, <<, >>, ~, ^, &, +, +@, -, -@, *, ** and so on.
Also all methods ending with a equals sign (where you can write obj.bla = blo
instead of obj.bla=(blo)).
HTH,
Sebastian
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