Create method using define_method with all sort of args?

Ruby
1

Hi all

I know that one can create new methods using define_method…

def new_method
end

is equivalent to

define_method(:new_method) do
end

def new_method(some_param)
end

is equivalent to

define_method(:new_method) do |some_param|
end

def new_method(some_param, *args)
end

is equivalent to

define_method(:new_method) do |some_param, *args|
end

But what’s equivalent to…

def new_method(some_param, options = {}, *args)
end

??? Thanks for help.
Josh

2

Oh yeah, forgot one…

def new_method(some_param, options = {}, *args, &block)
end

What’s the equivalent to this…?

3

On Nov 22, 6:52 am, Joshua M. [email protected] wrote:

What’s the equivalent to this…?

You have to use a predefined function if you want to pass a block,
e.g,

class A
def new_method1(somep, opts={}, *args, &block)
p opts
end
private
def _foo(somep, opts={}, *args, &block)
p opts
end
public
define_method(:new_method2, instance_method(:_foo))
end

Also, you can’t pass an optional argument to a block, you’d have to
write something like…

class A
define_method(:new_method3) { |somep, *args|
opts = {}
if args.length > 0 && args[0].class == Hash
opts = args[0]
end
p opts
}
end

Regards,
Jordan

4

On Nov 22, 2007, at 2:59 AM, Joshua M. wrote:

But what’s equivalent to…

def new_method(some_param, options = {}, *args)
end

define_method ‘new_method’ do |some_param, *argv|
options, *argv = argv
options ||= {}

…
end

a @ http://codeforpeople.com/

5

On Nov 23, 2:23 pm, “ara.t.howard” [email protected] wrote:

define_method ‘new_method’ do |some_param, *argv|
options, *argv = argv
options ||= {}

…
end

Ara,

Isn’t that dangerous in case new_method is called like:

a.new_method(“a”, other, args)

…where the optional ‘option’ arg is left out? It seems that your
version would consume the ‘other’ operand in that case. I think you’d
need to do something like I posted above to be safe.

Regards,
Joran

6

On Nov 23, 7:26 pm, MonkeeSage [email protected] wrote:

Isn’t that dangerous in case new_method is called like:

a.new_method(“a”, other, args)

…where the optional ‘option’ arg is left out? It seems that your
version would consume the ‘other’ operand in that case. I think you’d
need to do something like I posted above to be safe.

Your question implies to me that you think that if I define a method
like this:
def foo( name, age=0, weight=170 )
…
end
that I can then call it like this:
foo( “Gavin”, 175 ) # use default age.

In case I’m properly understanding you, then you should know that you
cannot do that. You can’t ‘skip’ an optional argument and have other
optional or non-optional arguments later. So, by definition, the
‘other’ you use in your example is necessarily the second parameter to
the method, and thus satisfies the OPs desired functionality.

7

On Nov 23, 10:16 pm, Phrogz [email protected] wrote:

In case I’m properly understanding you, then you should know that you
cannot do that.

Err…my brain broke for a minute there (bad brain!), heh. Thanks for
the correction.

Regards,
Jordan