Rails - Sep 2010 - unless params[:photo]['photo'].content_type =~ /^image/

In the "Rails cookbook", I read the following statement:

unless params[:photo][''photo''].content_type =~ /^image/

What do those parts mean?

* params[:photo][''photo'']?

* =~ /^image/

Thanks.
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On Mon, Sep 20, 2010 at 2:39 PM, Abder-Rahman Ali
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> In the "Rails cookbook", I read the following statement:
>
> unless params[:photo][''photo''].content_type =~ /^image/
>
> What do those parts mean?
It means you need to learn Ruby.
> * params[:photo][''photo'']?
params is a hash.  :photo is a key in the params hash.
> * =~ /^image/
=~ means match, as in regular expression matching.

/^image/ is a regular expression, it means "starts with
''image''".


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Thanks for your reply @Greg.

Regarding this part: params[:photo][''photo'']

What is [''photo'']?

Thanks.
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On Mon, Sep 20, 2010 at 2:48 PM, Abder-Rahman Ali
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> Regarding this part: params[:photo][''photo'']
>
> What is [''photo'']?
It''s probably from a file field:

<input type="file" name="photo[photo]" />



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Greg Donald wrote:
> On Mon, Sep 20, 2010 at 2:48 PM, Abder-Rahman Ali
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
> wrote:
>> Regarding this part: params[:photo][''photo'']
>>
>> What is [''photo'']?
> 
> It''s probably from a file field:
> 
> <input type="file" name="photo[photo]" />
> 
> 
> 
> --
> Greg Donald
> destiney.com | gregdonald.com
"photo" is originally a column field, but what does it mean when 
inserting it in this shape?

params[:photo][''photo'']

If params[:photo] is telling us that we have a key :photo, what is the 
use of [''photo''], this is what I''m not getting.

Thanks.

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On Mon, Sep 20, 2010 at 2:56 PM, Abder-Rahman Ali
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> "photo" is originally a column field, but what does it mean when
> inserting it in this shape?
>
> params[:photo][''photo'']
>
> If params[:photo] is telling us that we have a key :photo, what is the
> use of [''photo''], this is what I''m not getting.
It means there''s another hash inside the params[:photo] hash.

params[:photo]
<input type="file" name="photo" />

params[:photo][''photo'']
<input type="file" name="photo[photo]" />



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I see, thanks a lot.
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Just to make it more clear. When we say:

params[:photo]

This looks like follows in the "params" table:

------------------
   Key  |  Value
------------------
 :photo | "xyz"
------------------


How can this be represented in the params table?

params[:photo][''photo'']

Thanks.
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functions that return booleans( true or false), can end with a question mark
( ? )

and in ruby what is called a hash is a list of key value pairs, that is

:name => "abder", :id=> ''3''

that is a hash, if i want the value of name , call it like this

:name

that returns "abder", and hashes can be nested, like this

:params=> { :name => "abder", :id=> ''3''}

if i cal params directly i get ,

:name => "abder", :id=> ''3''

but if i want a value that is nested i do


params[:name]

and it returns

"abder"

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>
> params[:photo]
>
> This looks like follows in the "params" table:
>
> ------------------
>   Key  |  Value
> ------------------
>  :photo | "xyz"
> ------------------
>
>
not in the table in the params hash , when your app recives info back from
the user rails arranges it in a hash called parasm

look at you console log when ever you create a resource or dear an specific
one you will see

parameter => {  :id=>1, :name=>"blah" ....  }

to read from those nested values you call them  params[:id]

but that is how rails arrenges the request that has nothing to do with the
table.

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On Mon, Sep 20, 2010 at 4:12 PM, radhames brito
<rbritom-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> functions that return booleans( true or false), can end with a question
mark
> ( ? )
Any Ruby method name can end in a question mark, returning a boolean
is not required.

ruby-1.9.2-p0 > def foo?; return 1; end; foo?
 => 1


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@greg

inst that llike a convention, like if a method raises an exception the
developer can end ti with a bang  ( ! ).
if a method returns boolean doesnt the developer end it with ?  as a
convention?

is it or not convention?

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Thanks @radhames.

But, still, I cannot get the idea of:

params[:photo][''photo'']

And how it is represented.

Can you clarify on this?

Thanks.
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dont worry im reading the book right know to see what the code is about ,
ill reply in a few minutes

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Abder-Rahman Ali wrote:
> Thanks @radhames.
> 
> But, still, I cannot get the idea of:
> 
> params[:photo][''photo'']
> 
> And how it is represented.
> 
> Can you clarify on this?
What part of that syntax don''t you understand?

If the square brackets, review Hash syntax in Ruby.

If the nesting, read up on what Rails puts in the params hash.

Ask if you have further questions.
> 
> Thanks.
Best,
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dude , that some jurasick code, if from 2007?

wow, what the guy is down is checking the myme
type<http://www.iana.org/assignments/media-types/>on the create
action, today that is done in a validation in the model.

params[:photo][''photo'']

is something like this

parameter => {:item=>{:name=>"blah blah", :description=>
" more blah
blah"},:photo =>{:photo=>[ bunch of data about the file ] }   }

at the end in that bunch of that about the file the browser pases  the media
type, that is somethie the browser does and they can be

application <http://www.iana.org/assignments/media-types/application/>

audio <http://www.iana.org/assignments/media-types/audio/>

example <http://www.iana.org/assignments/media-types/examples/>

image <http://www.iana.org/assignments/media-types/image/>

message <http://www.iana.org/assignments/media-types/message/>

model <http://www.iana.org/assignments/media-types/model/>

multipart <http://www.iana.org/assignments/media-types/multipart/>

text <http://www.iana.org/assignments/media-types/text/>
video <http://www.iana.org/assignments/media-types/video/>

plus the images can be jpg or tiff

with    .content_type =~ /^image/

he is saying grab the media type see if it starts with image, as the browser
pases somthing like this

image/jpg

or

image/tiff

so with

unless params[:photo][''photo''].content_type =~ /^image/
flash[:error] =" that is not an image file "
render :action => ''new''
end

he is checking from the params hash if the file uploaded has a media type of
image. if not render new

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