"with" statement

Ruby
1

Pascal has a with statement. (I’m showing my age). It would be nice
instead of:

<td><%= h relationship.parent_id %></td>
<td><%= h relationship.link_type.pcln %></td>
<td><%= h relationship.child_id %></td>
<td><%= h relationship.active %></td>
<td><%= h relationship.notes %></td>
<td><%= h relationship.created_at %></td>
<td><%= h relationship.updated_at %></td>

I could do:

with(relationship) {
  <td><%= h parent_id %></td>
  <td><%= h link_type.pcln %></td>
  <td><%= h child_id %></td>
  <td><%= h active %></td>
  <td><%= h notes %></td>
  <td><%= h created_at %></td>
  <td><%= h updated_at %></td>
}

I bet there is a clever way to do this – I just don’t know now.

2

I don’t approve this solution, but why can’t you use it ?

<% %w{parent_id child_id active notes created_at updated_at}.each do |
attribute| %>

<%= h relationship.send( attribute.to_sym ) %> <% end %> <%h h relationship.link_type.pcln %>
3

On 10/21/07, Perry S. [email protected] wrote:

}

I bet there is a clever way to do this – I just don’t know now.

Posted via http://www.ruby-forum.com/.

You might want to have a look at instance_eval, I however feel that
the with statement was rather a weakness of Pascal.

HTH
Robert

4

Hi –

On Mon, 22 Oct 2007, Perry S. wrote:

}
You can use instance_eval:

david-a-blacks-computer:~ dblack$ erb
<% a = “hi” %>
<% a.instance_eval do %>
<%= upcase %>
<% end %>
^D

HI

David

5

Robert and David are right - you can use instance_eval. If you really
want with, it is very easy to add:

module Kernel
def with(object,&block)
object.instance_eval &block
end
end

with([1,2,3]) { length } # => 3

Dan Y.
http://dev.zeraweb.com/
Ruby And JavaScript Consulting

6

Dan Y. wrote:

Robert and David are right - you can use instance_eval. If you really
want with, it is very easy to add:

module Kernel
def with(object,&block)
object.instance_eval &block
end
end

with([1,2,3]) { length } # => 3

Dan Y.
http://dev.zeraweb.com/
Ruby And JavaScript Consulting

Yippie!!! I figured there was a way.

I think I also want for_with – but I can do that (I hope).

Thank you to all…

7

Dan Y. wrote:

Robert and David are right - you can use instance_eval. If you really
want with, it is very easy to add:

module Kernel
def with(object,&block)
object.instance_eval &block
end
end

with([1,2,3]) { length } # => 3

Dan Y.
http://dev.zeraweb.com/
Ruby And JavaScript Consulting

Why not just alias instance_eval? Would achieve the same and is less
overhead.

Regards
Stefan

8

On Oct 22, 7:48 am, Stefan R. [email protected] wrote:

with([1,2,3]) { length } # => 3
Stefan
–
Posted viahttp://www.ruby-forum.com/.

Probably because it wouldn’t read right anymore.

“With [this object] do [some stuff]” reads naturally, whereas “[this
object] with [some stuff]” is somewhat strange.

9

module Kernel
def with(object,&block)
object.instance_eval &block
end
end

with([1,2,3]) { length } # => 3

This is really neat and compact. I love it. I think using eval that
much probably results in performance costs, but I’m definitely going
to add this to my .irbrc.

–
Giles B.

Blog: http://gilesbowkett.blogspot.com
Portfolio: http://www.gilesgoatboy.org
Tumblelog: http://giles.tumblr.com/

10

On 21/10/2007, Dan Y. [email protected] wrote:

module Kernel
def with(object,&block)
object.instance_eval &block
end
end

with([1,2,3]) { length } # => 3

You could even do something like this:

module Kernel
def with_block(*args, &block)
send(*args) { |obj| obj.instance_eval &block }
end
end

[‘asdf’, ‘jkl’, ‘semicolon’].with_block(:map) { length } # => [4, 3, 9]

That would allow something like this:
<% with_block(:form_for, :user, @user) { %>
<%= text_field :name %>
<%= text_field :email %>
<%= password_field :password %>
<% } %>

It may or may not be useful, but it’s fun.

11

2007/10/22, Giles B. [email protected]:

module Kernel
def with(object,&block)
object.instance_eval &block
end
end

with([1,2,3]) { length } # => 3

This is really neat and compact.

How is this more compact than

[1,2,3].length

?

Cheers

robert

12

On 10/23/07, Robert K. [email protected] wrote:

How is this more compact than

[1,2,3].length

?

Check the rest of the thread.

–
Giles B.

Blog: http://gilesbowkett.blogspot.com
Portfolio: http://www.gilesgoatboy.org
Tumblelog: http://giles.tumblr.com/

13

I may really be misremembering the with statement from Pascal, but, as I
recall it was more of a namespace / shortcut kind of thing.

For example:

If you have a data structure named Person, which has a bunch of fields
within
it, like FirstName, LastName, Address, …

You could either assign data to those fields with syntax something like
(that
was a long time ago, and I’m getting old):

Person.FirstName := William
Person.LastName := Smith
…

or you could use the with statement, something like this:

with Person begin
FirstName := William
LastName := Smith
…
end

(Sorry about the syntax errors that I know must be there–like I said,
it was
a long time ago. Oh, yeah–semicolons! And keywords in all caps!
Forgetting
can be good :wink:

I guess my point is, in these discussions about finding a way to
simulate the
Pascal “with” statement in Ruby, it doesn’t seem like you (a very
generic
you) are targetting the with functionality from Pascal.

On the other hand, I suspect there must be ways of doing that in Ruby–I
just
can’t think of those atm.

Randy K.