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harm

2007-Jul-14 12:24 UTC

Symbols are puzzling me and not only symbols

Dear all,
I''ve got two burning questions. Both regard the manipulation of the
params hash.
Imagine:
params = {"commit"=>"Add comment",
"comment"=>{"message"=>"foo",
"name"=>"bar", "answer"=>"2",
"email"=>"foo@bar"}}

So the params hash has two keys, one(''commit'') points to a
string the
other(''comment'') to an other hash.
Normally I can do something like; params[:id] or whatever, now if I do
that, params[:commit] it returns nil! Why?? params[''commit'']
works as
expected.

On to the second question, when I have a large array or hash I used
to(In Java/PHP etc) split them up in several lines. For example:
    tmp = {:message => ''tmp'' ,:name =>
''tmp'' ,:email => ''tmp''}

Would become:
    tmp = {  :message => ''tmp''
               ,:name => ''tmp''
               ,:email => ''tmp''
             }

I find this eaasier to read and easier to check for comma related
errors. However Ruby fails to recognise this, failing with the error:
syntax error, unexpected '','', expecting ''}''
          ,:name => ''tmp''
           ^

Ruby is better kidding me. The interpreter doesn''t handle whitespace??
Any comments on what I am doing wrong or why not ignoring whitespace
is a good idea, I''d love to hear.

With kind regads


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Matthew Rudy

2007-Jul-14 12:36 UTC

head link

Re: Symbols are puzzling me and not only symbols

ah...
what you experienced before with params["id"] and params[:id] returned
the same,
was in fact the magic of rails,

and the HashWithIndifferentAccess,
and extension of hash,
which reacts indifferently to symbols vs. strings.

try;
params = HashWithIndifferentAccess.new
params[:id] = "this is the id"

params["id"] will return "this is the id"
params[:id] will return "this is the id"

-----

alternatively.

params = {:id => "this is the id", :commit => "this is the 
commit"}.with_indifferent_access.

-----
harm wrote:> Dear all,
> I''ve got two burning questions. Both regard the manipulation of
the
> params hash.
> Imagine:
> params = {"commit"=>"Add comment",
"comment"=>{"message"=>"foo",
> "name"=>"bar", "answer"=>"2",
"email"=>"foo@bar"}}
> 
> So the params hash has two keys, one(''commit'') points to
a string the
> other(''comment'') to an other hash.
> Normally I can do something like; params[:id] or whatever, now if I do
> that, params[:commit] it returns nil! Why??
params[''commit''] works as
> expected.
-- 
Posted via http://www.ruby-forum.com/.

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Matthew Rudy

2007-Jul-14 12:41 UTC

head link

Re: Symbols are puzzling me and not only symbols

Yeah, ruby doesn''t care about spaces, but it does care about new lines.
Which is good, at least it doesn''t rely on semi-colons.

for a multiline declaration with clarity of commas

tmp = {
    :message => ''tmp''  ,
    :name    => ''tmp''  ,
    :email   => ''tmp''
    }
> On to the second question, when I have a large array or hash I used
> to(In Java/PHP etc) split them up in several lines. For example:
>     tmp = {:message => ''tmp'' ,:name =>
''tmp'' ,:email => ''tmp''}
> 
> Would become:
>     tmp = {  :message => ''tmp''
>                ,:name => ''tmp''
>                ,:email => ''tmp''
>              }
> 
> I find this eaasier to read and easier to check for comma related
> errors. However Ruby fails to recognise this, failing with the error:
> syntax error, unexpected '','', expecting
''}''
>           ,:name => ''tmp''
-- 
Posted via http://www.ruby-forum.com/.

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dblack-TKXtfPMJ4Ozk1uMJSBkQmQ@public.gmane.org

2007-Jul-14 13:03 UTC

head link

Re: Symbols are puzzling me and not only symbols

Hi --

On Sat, 14 Jul 2007, Matthew Rudy wrote:
>
> Yeah, ruby doesn''t care about spaces, but it does care about new
lines.
> Which is good, at least it doesn''t rely on semi-colons.
There are some cases where spaces matter; for example:

irb(main):002:0> puts (3) + 2
5
=> nil
irb(main):003:0> puts(3) + 2
3
NoMethodError: undefined method `+'' for nil:NilClass

In the second one, it evaluated puts(3) (including actually puts''ing
3) and then tries to add 2 to it, which fails.

Also:

irb(main):004:0> puts puts (3)
(irb):4: warning: don''t put space before argument parentheses
3
nil

which does the same as puts puts(3) but gives you that warning.
> for a multiline declaration with clarity of commas
>
> tmp = {
>    :message => ''tmp''  ,
>    :name    => ''tmp''  ,
>    :email   => ''tmp''
>    }
At the very great risk of sounding curmudgeonly, could I put in a
heartfelt plea for people not to do that?  It looks bizarre, and seems
to invite scrutiny in case there''s been some kind of mistake or
omission.


David

-- 
* Books:
   RAILS ROUTING (new! http://www.awprofessional.com/title/0321509242)
   RUBY FOR RAILS (http://www.manning.com/black)
* Ruby/Rails training
     & consulting:  Ruby Power and Light, LLC (http://www.rubypal.com)

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Matthew Rudy

2007-Jul-14 13:18 UTC

head link

Re: Symbols are puzzling me and not only symbols

> 
>> for a multiline declaration with clarity of commas
>>
>> tmp = {
>>    :message => ''tmp''  ,
>>    :name    => ''tmp''  ,
>>    :email   => ''tmp''
>>    }
> 
> At the very great risk of sounding curmudgeonly, could I put in a
> heartfelt plea for people not to do that?  It looks bizarre, and seems
> to invite scrutiny in case there''s been some kind of mistake or
> omission.
To be honest,
the way I like to declare hashes is like this;

tmp = {
    :message => "tmp",
        :name => "tmp",
            :email => "tmp",
                }

that''s how I like it.

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

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harm

2007-Jul-15 09:42 UTC

head link

Re: Symbols are puzzling me and not only symbols

Aha, but why does that scheme break down? Knowing that would prevent
me from running future problems. The class documentation()http://
api.rubyonrails.org/classes/HashWithIndifferentAccess.html) does not
bring me very far either. Especially the line:
[quote]
this class has dubious semantics and we only have it so that people
can write params[:key] instead of params[''key'']
[/quote]
does not inspire confidence.

On Jul 14, 2:36 pm, Matthew Rudy
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:> ah...
> what you experienced before with params["id"] and params[:id]
returned
> the same,
> was in fact the magic of rails,
>
> and the HashWithIndifferentAccess,
> and extension of hash,
> which reacts indifferently tosymbolsvs. strings.
>
> try;
> params = HashWithIndifferentAccess.new
> params[:id] = "this is the id"
>
> params["id"] will return "this is the id"
> params[:id] will return "this is the id"
>
> -----
>
> alternatively.
>
> params = {:id => "this is the id", :commit => "this is
the
> commit"}.with_indifferent_access.
>
> -----
>
> harm wrote:
> > Dear all,
> > I''ve got two burning questions. Both regard the manipulation
of the
> > params hash.
> > Imagine:
> > params = {"commit"=>"Add comment",
"comment"=>{"message"=>"foo",
> > "name"=>"bar",
"answer"=>"2",
"email"=>"foo@bar"}}
>
> > So the params hash has two keys, one(''commit'')
points to a string the
> > other(''comment'') to an other hash.
> > Normally I can do something like; params[:id] or whatever, now if I do
> > that, params[:commit] it returns nil! Why??
params[''commit''] works as
> > expected.
>
> --
> Posted viahttp://www.ruby-forum.com/.

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harm

2007-Jul-15 09:44 UTC

head link

Re: Symbols are puzzling me and not only symbols

Hmmm, alright. I still don''t understand why the parser does not just
run until it encounters an other curly brace (}). But I can live with
it.

On Jul 14, 2:41 pm, Matthew Rudy
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:> Yeah, ruby doesn''t care about spaces, but it does care about new
lines.
> Which is good, at least it doesn''t rely on semi-colons.
>
> for a multiline declaration with clarity of commas
>
> tmp = {
>     :message => ''tmp''  ,
>     :name    => ''tmp''  ,
>     :email   => ''tmp''
>     }
>
> > On to the second question, when I have a large array or hash I used
> > to(In Java/PHP etc) split them up in several lines. For example:
> >     tmp = {:message => ''tmp'' ,:name =>
''tmp'' ,:email => ''tmp''}
>
> > Would become:
> >     tmp = {  :message => ''tmp''
> >                ,:name => ''tmp''
> >                ,:email => ''tmp''
> >              }
>
> > I find this eaasier to read and easier to check for comma related
> > errors. However Ruby fails to recognise this, failing with the error:
> > syntax error, unexpected '','', expecting
''}''
> >           ,:name => ''tmp''
>
> --
> Posted viahttp://www.ruby-forum.com/.

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harm

2007-Jul-15 09:45 UTC

head link

Re: Symbols are puzzling me and not only symbols

Interesing example! I should use that in class. Thanks.

On Jul 14, 3:03 pm, dbl...-TKXtfPMJ4Ozk1uMJSBkQmQ@public.gmane.org
wrote:> Hi --
>
> On Sat, 14 Jul 2007, Matthew Rudy wrote:
>
> > Yeah, ruby doesn''t care about spaces, but it does care about
new lines.
> > Which is good, at least it doesn''t rely on semi-colons.
>
> There are some cases where spaces matter; for example:
>
> irb(main):002:0> puts (3) + 2
> 5
> => nil
> irb(main):003:0> puts(3) + 2
> 3
> NoMethodError: undefined method `+'' for nil:NilClass
>
> In the second one, it evaluated puts(3) (including actually
puts''ing
> 3) and then tries to add 2 to it, which fails.
>
> Also:
>
> irb(main):004:0> puts puts (3)
> (irb):4: warning: don''t put space before argument parentheses
> 3
> nil
>
> which does the same as puts puts(3) but gives you that warning.
>
> > for a multiline declaration with clarity of commas
>
> > tmp = {
> >    :message => ''tmp''  ,
> >    :name    => ''tmp''  ,
> >    :email   => ''tmp''
> >    }
>
> At the very great risk of sounding curmudgeonly, could I put in a
> heartfelt plea for people not to do that?  It looks bizarre, and seems
> to invite scrutiny in case there''s been some kind of mistake or
> omission.
>
> David
>
> --
> * Books:
>    RAILS ROUTING (new!http://www.awprofessional.com/title/0321509242)
>    RUBY FOR RAILS (http://www.manning.com/black)
> * Ruby/Rails training
>      & consulting:  Ruby Power and Light, LLC (http://www.rubypal.com)

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Rails - Jul 2007 - Symbols are puzzling me and not only symbols

Symbols are puzzling me and not only symbols

Re: Symbols are puzzling me and not only symbols

Re: Symbols are puzzling me and not only symbols

Re: Symbols are puzzling me and not only symbols

Re: Symbols are puzzling me and not only symbols

Re: Symbols are puzzling me and not only symbols

Re: Symbols are puzzling me and not only symbols

Re: Symbols are puzzling me and not only symbols