Method missing and arrays as arguments

Ruby
1

How do you go about passing arrays as arguments to something like
method_missing? I’ve got a method that takes an array as an argument,
but calling it via method_missing is proving problematic. How do you
deal with arrays in these situations?

def table_row(values)
# values is the list of items in the table row
#…
end

def method_missing(method,*args)
if respond_to?method.to_s[/^add_([^$]+)/,1]
@data<<method(method.to_s[/^add_([^$]+)/,1]).call(*args)
else
super method_missing(method,*args)
end
end

–Kyle

2

On Apr 6, 2009, at 4:35 PM, Kyle S. wrote:

end
end

I think your problem is in the else clause. It should be:

else

super
end

You don’t want to call method_missing explicitly, you’ll create an
infinite recursion.

3

On Mon, Apr 6, 2009 at 4:35 PM, Kyle S. [email protected]
wrote:

def method_missing(method,*args)
if respond_to?method.to_s[/^add_([^$]+)/,1]
@data<<method(method.to_s[/^add_([^$]+)/,1]).call(*args)
else
super method_missing(method,*args)
end
end

I’m not sure exactly what you are trying to do, I’m guessing that if you
send add_table_row(some_array) to an instance, the method_missing will
call
table_row and add the result to @data.

The problem isn’t the array argument, it’s what you are doing in the
true
leg of the if.

The first argument to method_missing is not a method, but a symbol. You
are
converting this symbol to a string, stripping off add_ from the
beginning
and they trying to call the string, which ain’t gonna work.

Instead you want to use send:

class SomeClass
attr_reader :data

def table_row(values)
# values is the list of items in the table row
#…
values
end

def method_missing(symbol,*args)
without_add = symbol.to_s[/^add_([^$]+)/,1]
if respond_to? without_add
@data ||= []
@data<< send(without_add, *args)
else
super method_missing(method,*args)
end
end
end

sc = SomeClass.new
sc.add_table_row([1,2,3])
sc.data # => [[1, 2, 3]]

I used lazy initialization to initialize @data, assuming that this is
vaguely what you are after.

–
Rick DeNatale

Blog: http://talklikeaduck.denhaven2.com/
Twitter: http://twitter.com/RickDeNatale
WWR: http://www.workingwithrails.com/person/9021-rick-denatale
LinkedIn: http://www.linkedin.com/in/rickdenatale

4

Ok, I found my issue, it was rather dense of me to be honest, it had
to do with how I was calling it.

That said, this is what I came up with

def method_missing(method,*args)
without_add=method.to_s[/^add_([^$]+)/,1]
if not(without_add.empty?) and respond_to?without_add
#calling the string worked (I’m guessing it tries a .to_sym)
#@data<<method(without_add).call(*args)
# Still, this is prettier
@data<<send(without_add,*args)
else
super
end
end

5

On Mon, Apr 6, 2009 at 5:00 PM, Gary W. [email protected] wrote:

  @data<<method(method.to_s[/^add_([^$]+)/,1]).call(*args)

   super

end

You don’t want to call method_missing explicitly, you’ll create an infinite
recursion.

Well, that’s another problem, which I overlooked in MY response.

–
Rick DeNatale

Blog: http://talklikeaduck.denhaven2.com/
Twitter: http://twitter.com/RickDeNatale
WWR: http://www.workingwithrails.com/person/9021-rick-denatale
LinkedIn: http://www.linkedin.com/in/rickdenatale

6

Oh, and I forgot to say, thanks, it did help a ton.