Fun with setter functions

Ruby
1

I have a setter function in a class that I would like to pass additional
arguments to, so I can do some addtional calculations if required.

My first crack at this was to do something like…

…
def variable=(value, options=nil)
@variable = value
do_something_cool if options == :flag
end

Here’s the only problem, how do you pass the options?

object.variable = value, :flag
results in
[value, :flag] being passed to the function.

I see a couple of work arounds.

  1. send works, but is ugly object.send(‘variable=’,value,:flag)
  2. rewrite variable so that it expects an array and just unpack stuff
    from the array

Any other solutions I may have overlooked?

_Kevin
www.sciwerks.com

2

On 8/26/06, Kevin O. [email protected] wrote:

Any other solutions I may have overlooked?

Try

def variable=(*args)
@variable = args.shift
do_something_cool if args.shift == :flag
end

*args will receive array of arguments passed in either case (i.e. both
when one and two parameters are passed)

The latter args.shift will return nil if there are no more parameters.

Another possibility could be using hash parameters, as rails often does:

def variable=(value, options ={})
@variable = value
do_something_cool if options[:options] == :flag
end

Call as: variable = value, :options => :flag

3

On 26.08.2006 16:42, Jan S. wrote:

end
from the array
*args will receive array of arguments passed in either case (i.e. both

Call as: variable = value, :options => :flag

Both approaches won’t work as Ruby does allow only exactly one argument
to an assignment:

11:06:12 [Temp]: cat -n var.rb
1
2 class Foo
3 def var=(val,*opts)
4 p opts
5 @var = val
6 end
7
8 def var() @var end
9 end
10
11 f=Foo.new
12 p f.var
13 f.var = 10
14 p f.var
15 f.var = 10, 20
11:06:18 [Temp]: ruby var.rb
nil
[]
10
[]

You can get it to work with send but then you’re loosing the clean
syntax:

11:07:03 [Temp]: cat -n var.rb
1
2 class Foo
3 def var=(val,*opts)
4 p opts
5 @var = val
6 end
7
8 def var() @var end
9 end
10
11 f=Foo.new
12 p f.var
13 f.var = 10
14 p f.var
15 f.var = 10, 20
16 p f.var
17 f.send(:var=, 10, :opt => 20)
11:08:08 [Temp]: ruby var.rb
nil
[]
10
[]
[10, 20]
[{:opt=>20}]
11:08:08 [Temp]:

Kind regards

robert