Method_missing and assignment

ruby-talk
1

Hi,

with ruby 1.8.2:

···

--------------------------------------------------
class A
  def method_missing (a,*b)
    # do something
  end
end

a=A.new
a.foo("bar","baz")
a.foo=("bar","baz")
--------------------------------------------------

the last line gives me an error

-:11: syntax error
a.foo=("bar","baz")
             ^

Any way I can assign multiple values in a natural way with
method_missing? Or would you suggest to use an array that holds
multiple data?

Regards,

Patrick

2

Patrick Gundlach wrote:

Hi,

with ruby 1.8.2:
--------------------------------------------------
class A
  def method_missing (a,*b)
    # do something
  end
end

a=A.new
a.foo("bar","baz")
a.foo=("bar","baz")
--------------------------------------------------

the last line gives me an error

-:11: syntax error
a.foo=("bar","baz")
             ^

Any way I can assign multiple values in a natural way with
method_missing? Or would you suggest to use an array that holds
multiple data?

Regards,

Patrick

It's not particularly a property of method_missing--you can't even define a method to do this:

irb(main):001:0> def foo=(a,b); end
=> nil
irb(main):002:0> self.foo=(1,2)
SyntaxError: compile error
(irb):2: syntax error
self.foo=(1,2)
              ^
         from (irb):2
irb(main):003:0>

3

a.foo = ["bar","baz"];

You cannot have more than one value on the right side of a call to a method whose name ends in =.

(But you can do:
   a.foo, b.foo = "bar", "baz"
which is the same as:
a.foo = "bar"
b.foo = "baz"

···

On Jun 3, 2005, at 2:05 PM, Patrick Gundlach wrote:

the last line gives me an error

-:11: syntax error
a.foo=("bar","baz")
             ^

4

[...]

It's not particularly a property of method_missing--you can't even
define a method to do this:

irb(main):002:0> self.foo=(1,2)
SyntaxError: compile error
(irb):2: syntax error
self.foo=(1,2)
              ^
         from (irb):2

I should have tested the obvoius, thanks for this out.

but something like method=(1,2) could be handy, for example for
assigning complex numbers.

Thanx,

Patrick

5

--- Patrick Gundlach <clr5.10.randomuser@spamgourmet.com>
wrote:

[...]

> It's not particularly a property of method_missing--you
can't even
> define a method to do this:
>
> irb(main):002:0> self.foo=(1,2)
> SyntaxError: compile error
> (irb):2: syntax error
> self.foo=(1,2)
> ^
> from (irb):2

I should have tested the obvoius, thanks for this out.

but something like method=(1,2) could be handy, for example
for
assigning complex numbers.

Thanx,

Patrick

The above isn't valid syntax because it is being parsed as an
assignment (not a method call) and (1,2) is not a valid
expression (RHS).

If you need something more complex, you can just assign with an
array:

self.foo = [1,2]

There is an RCR open to attempt to be able to do this type of
thing:

self.foo(*args) = value

which gets interpreted as self."foo="(*args,value). This is
similar to the = operator.

···

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6

[...]

The above isn't valid syntax because it is being parsed as an
assignment (not a method call) and (1,2) is not a valid
expression (RHS).

OK, I see.

If you need something more complex, you can just assign with an
array:

self.foo = [1,2]

This is the solution where I first thought of as a workaround. But it
looks ok to me now.

Thanks,

Pat