Case menu - obtain the first conditions?

Ruby
1

Hi.

Consider I have a case menu like this.

def enter_menu
case @i
when ‘list_cars’,‘lc’
list_cars
when ‘list_horses’,‘lh’
list_horses
when ‘list_plants’,'lp
list_plants
when ‘help’
show_help
end
end

Now, inside the method show_help, I would like to
call the FIRST entry on each case menu.

I.e: list_cars list_horses and list_plants

Is there a way to do this easily?

The actual case menu is very very long, with multiple aliases.
But the main name of every when entry is always the first entry.

In other words I would need a way to programmatically access the
first option of every when clause.

2

On Jan 15, 1:36am, Marc H. [email protected] wrote:

when ‘list_plants’,'lp

Is there a way to do this easily?

The actual case menu is very very long, with multiple aliases.
But the main name of every when entry is always the first entry.

In other words I would need a way to programmatically access the
first option of every when clause.

Don’t use a case statement.

You could use a hash, something like

def menu_options
options = {
‘list_cars’ => proc { list_cars }, ‘lc’ => ‘list_cars’,
‘list_horses’ => proc { list_horses }, ‘lh’ => ‘list_horses’,
‘list_plants’ => proc { list_plants }, ‘lp’ => ‘list_plants’,
‘help’ => proc { show_help }
}
options.default = proc { show_help }
options
end

def enter_menu
option = @i
action = nil

until action.respond_to?(:call)
  action = menu_options[option]
  option = action
end

action.call

end

def show_help
options = menu_options
main_options = options.keys.select { |k| options[k].respond_to?
(:call) }

puts "The real options are #{main_options.inspect}"

end

This could be much improved, but that’s the general idea.

3

options = {
‘list_cars’ => proc { list_cars }, ‘lc’ => ‘list_cars’,
‘list_horses’ => proc { list_horses }, ‘lh’ => ‘list_horses’,
‘list_plants’ => proc { list_plants }, ‘lp’ => ‘list_plants’,
‘help’ => proc { show_help }
}
options.default = proc { show_help }
options

Hmm.

The problem is that I would be forced to use procs?

I don’t like that.

I also feel as if the way to use aliases as in your example is VERY
cumbersome with hashes.

when ‘list_cars’,‘lc’

Is much more readable.

Or a way to programmatically access your methods:

self.methods # => [“list_cars”, “list_whatever”, “list_plants”, …]

A better way would probably be:
self.class.public_instance_methods(false)

Hmm actually, you gave me a very good idea. I will probably toy a little
bit with that - I could follow with a convention of methods for
instance, or otherwise denote primary methods. Thanks Ryan!

By the way, also thanks to you Yossef M… Even if I initially
disliked your suggestion, I will continue to play with it and test it
slowly (which may help me to convince myself that it may not be so ugly
as it appears to be on first glance).

Thanks!

4

On Jan 14, 2012, at 22:36 , Marc H. wrote:

In other words I would need a way to programmatically access the
first option of every when clause.

Or a way to programmatically access your methods:

self.methods # => [“list_cars”, “list_whatever”, “list_plants”, …]

A better way would probably be:
self.class.public_instance_methods(false)