Baffled by single quote in eval

Rails
1

I am trying to understand how to work with a single quote within an eval
such as:

assigned_string = ‘’
name = “Addy’s”
eval(“assigned_string=’#{name}’”)

SyntaxError: (eval):1: syntax error, unexpected tIDENTIFIER, expecting
$end
assigned_string=‘Addy’s’
^
Ok, this error makes sense, but when I try to escape the single quote I
also
get an error:

eval(“assigned_string=’#{name.gsub(/’/,”’")}’")
SyntaxError: (eval):1: syntax error, unexpected tIDENTIFIER, expecting
$end
assigned_string=‘Addy’s’

However if I want to just remove the single quote I am fine and get no
error:
eval(“assigned_string=’#{name.gsub(/’/,”")}’")

Is there a different way to do such an eval? In actuality what I am
doing
with this phrase is to assign hash params to the attributes of a class:

eval(“background_process_status.#{key.to_s}=’#{value}’”)

2

On Sat, Apr 9, 2011 at 10:37 PM, David K.
[email protected]wrote:

Ok, this error makes sense, but when I try to escape the single quote I

Is there a different way to do such an eval? In actuality what I am doing
with this phrase is to assign hash params to the attributes of a class:

eval(“background_process_status.#{key.to_s}=‘#{value}’”)

Does it need to use eval? If not, you can just:

background_process.send(“#{key.to_s}=”, value)

3

try this
eval(“assigned_string=#{name}”),am not sure may be it 'l work

4

On Apr 9, 11:37pm, David K. [email protected] wrote:

Is there a different way to do such an eval? In actuality what I am doing
with this phrase is to assign hash params to the attributes of a class:

eval(“background_process_status.#{key.to_s}=‘#{value}’”)

I’d highly recommend that you not do this. Using send is not only
more efficient, it’s far safer - for instance, what happens if
somebody sends your code a value like

‘; rm -rf *;’

This will be syntactically valid, and will make quite a mess…

–Matt J.

5

On Sun, Apr 10, 2011 at 9:51 AM, Matt J. [email protected] wrote:

somebody sends your code a value like

‘; rm -rf *;’

This will be syntactically valid, and will make quite a mess…

Thanks all… yeah, I will use send, I forgot about that and you are
right,
it gets yucky very fast when things like single quotes and who knows
what
else get added.

Also, on this answer: eval(“assigned_string=#{name}”) , no it does not
work,
this is what I had originally but if you output the internal string it
looks
like “assigned_string=david” which of course errors out unless what is
in
‘name’ is a non string type.

6

On Sun, Apr 10, 2011 at 10:43 AM, Frederick C. <
[email protected]> wrote:

Thanks all… yeah, I will use send, I forgot about that and you are
right,
it gets yucky very fast when things like single quotes and who knows what
else get added.

For what it’s worth I suspect that the problem was that you needed to
escape the \ in your substitution ( ie “\’”)

I just tried this and thought for sure you were right. But no! So let me
step back, really I fail to understand why if I have a param[key] value
of
“Addy’s” that Ruby can not handle it on its own, and much less escaped
by
("’" or “\’”):

account.name = “Addy’s”
BackgroundProcessStatus.update(:status => “Processing Account name: #{
account.name}”)

class BackgroundProcessStatus < ActiveRecord::Base
def self.update(params)
background_process_status = BackgroundProcessStatus.first ||
BackgroundProcessStatus.new
params.keys.each do |key|
background_process_status.send("#{key.to_s}=", params[key])
end
end
end

The delayed_job output is:
SyntaxError: (eval):2: syntax error, unexpected tIDENTIFIER, expecting
$end
…Processing Account name: Addy’s Harbor Dodge’
^ - 0 failed attempts

I dont know if this has to do with it running as a job but if so in the
dark
as to why that would be as this seems to be pretty basic Ruby.

7

On Apr 10, 4:38pm, David K. [email protected] wrote:

somebody sends your code a value like

‘; rm -rf *;’

This will be syntactically valid, and will make quite a mess…

Thanks all… yeah, I will use send, I forgot about that and you are right,
it gets yucky very fast when things like single quotes and who knows what
else get added.

For what it’s worth I suspect that the problem was that you needed to
escape the \ in your substitution ( ie “\'”)

Fred

8

On Sun, Apr 10, 2011 at 11:06 AM, David K.
[email protected]wrote:

On Apr 9, 11:37 pm, David K. [email protected] wrote:

For what it’s worth I suspect that the problem was that you needed to
escape the \ in your substitution ( ie “\'”)

I just tried this and thought for sure you were right. But no! So let me
step back, really I fail to understand why if I have a param[key] value of
“Addy’s” that Ruby can not handle it on its own, and much less escaped by
(“'” or “\'”):

I found the problem — seems that the delayed_job process must be
restarted
if code is updated. I had updated the code but the old code was
seemingly
being executed.

9

Hi David,

On 10 Apr 2011, at 04:37, David K. wrote:

Is there a different way to do such an eval? In actuality what I am doing with
this phrase is to assign hash params to the attributes of a class:

eval(“background_process_status.#{key.to_s}=’#{value}’”)

Assuming you have attribute writers defined for your attributes:

background_process_status.send("#{key}=", value)

would be better, I think.

Regards,

Tony.