3 newbie questions

hey all,
I have 3 tables like this:
Images (id,name)
Tags (id,name)
ImagesTags(imageid,tagid)

in my image model I do a “has_and_belongs_to_many :tags” but to make
it work I need to rename ImagesTags(imageid,tagid) to
Images_Tags(image_id,tag_id). My question is that given that I can’t
rename the table, is there any way to make it work with the original
names?

Second question:
I have 2 tables like this:
Picture(id,name,albumid)
Albums(id,name)

in my Picture model I put:
belongs_to :album, :foreign_key => “dirid”

and in my Album model I put:
has_many :images

Yet, in my album/list.rhtml when I put :

<% for picture in album.pictures %> <%= picture.name %> <% end %>

I get:
SQLite3::SQLException: no such column: pictures.album_id: SELECT *
FROM pictures WHERE (pictures.album_id = 1)

so it looks like the :foreign_key => “dirid” is ignored. Any idea
what I could make it work?

Third question:
I would like to right some code that would work like this:
<% if thumbnail-file.jpg doesn’t exists execute create_thumbnail()
file.jpg %>

I already have the create_thumbnail() working. Any idea how to write
this right?

thanx in advance

Pat

Hi Pat!

On 17/07/2006, at 10:50 AM, Patrick A. wrote:

names?

You don’t have to rename your table, make your habtm declaration look
like this:

has_and_belongs_to_many :tags, :join_table => ‘ImagesTags’

so it looks like the :foreign_key => “dirid” is ignored. Any idea
what I could make it work?

On your Album model you need to specify the foriegn_key as well
afaik, try:

has_many :pictures, :foreign_key => ‘dirid’

Third question:
I would like to right some code that would work like this:
<% if thumbnail-file.jpg doesn’t exists execute create_thumbnail()
file.jpg %>

I already have the create_thumbnail() working. Any idea how to
write this right?

Could you explain this one a bit further?

Ryan.

right?
1st check if /thumbnail/thumbi.jpg exists
2nd if it doesn´t it should execute the function create_thumbnail() file.jpg
3rd if it already exists do nothing

what I want to do is check if a file exists in a given directory and
if it doesn´t then execute the function that creates it (that function
to create the file is already written).

<% unless File.exist?(RAILS_ROOT + “/thumbnail.thumbi.jpg”)
create_thumbnail()
end
%>
<%= image_tag(…) %>

Although if you know the thumbnail you’re looking for before you get to
your view (and I think you would) I’d do the creation in your
controller.

Also, just something to keep in mind. What if two people hit that page
at
the exact same time and your create_thumbnail() method gets called twice
at the exact same time? Will the thumbnail get written out correctly?

-philip

On 7/17/06, Ryan A. [email protected] wrote:

Third question:

I would like to right some code that would work like this:

<% if thumbnail-file.jpg doesn’t exists execute create_thumbnail() file.jpg
%>

I already have the create_thumbnail() working. Any idea how to write this
right?

Could you explain this one a bit further?

Ryan.
Thanx a lot for your answers Ryan. About the third question, I want to
display thumbnails that are in /thumbnails of images that are in my
/image. The thing is that if there is no thumbnail for a given image I
want to create it but if the thumnail exists it is not necessary to
recreate it.
so the code should:
1st check if /thumbnail/thumbi.jpg exists
2nd if it doesn´t it should execute the function create_thumbnail()
file.jpg
3rd if it already exists do nothing

what I want to do is check if a file exists in a given directory and
if it doesn´t then execute the function that creates it (that function
to create the file is already written).

thanx in advance

Pat

On 7/18/06, Philip H. [email protected] wrote:

right?
1st check if /thumbnail/thumbi.jpg exists
%>
<%= image_tag(…) %>

Although if you know the thumbnail you’re looking for before you get to
your view (and I think you would) I’d do the creation in your controller.

Also, just something to keep in mind. What if two people hit that page at
the exact same time and your create_thumbnail() method gets called twice
at the exact same time? Will the thumbnail get written out correctly?

thanx for your answer. I guess that if two people access the site at
the same time the first thumbnail will be overwritten by the second or
no? is there a way to secure that kind of situation other than forcing
the admin to generate thumbnails first?

On 7/16/06, Ryan A. [email protected] wrote:

Images (id,name)
Images_Tags(image_id,tag_id). My question is that given that I can’t
has_and_belongs_to_many :tags, :join_table => ‘ImagesTags’

thanx but I still have to rename my column imageid to image_id and tagid
to
tag_id. Any idea how I could make it work with these column names?

thanx in advance

Pat

right?
1st check if /thumbnail/thumbi.jpg exists
end
thanx for your answer. I guess that if two people access the site at
the same time the first thumbnail will be overwritten by the second or
no? is there a way to secure that kind of situation other than forcing
the admin to generate thumbnails first?

Does an admin upload the images using a web form? If so, generate the
thumbnail then. Otherwise, generate it and put it in a temporary file.
Then move the file into place. That’s usually an atomic transaction so
you won’t have to worry about a garbled file. You’ll still generate it
twice though, but at least they won’t clobber each other and give you an
unusuable file…

-philip

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