Get selected value from a collection_select

Rails
1

I have an edit form and I need to get the SELECTED VALUE from a
collection_select in a variable.

So if I have this…

<%= f.collection_select :part_id, @parts, :id, :cost_and_name, :prompt
=> “Select” %>

How can I peek inside and get, for example, the part_id?

2

Leonel . wrote in post #1018324:

I have an edit form and I need to get the SELECTED VALUE from a
collection_select in a variable.

So if I have this…

<%= f.collection_select :part_id, @parts, :id, :cost_and_name, :prompt
=> “Select” %>

How can I peek inside and get, for example, the part_id?

Okay, look at this:

| | | |
| browser| 2) | server |
| | <— response – | |
±-------+ (html page) ------------
3) User makes 1) ruby code
a selection executes

What you are asking is: “In step 1, can I peek and get the user’s
selection?” The answer, obviously, is no. The ruby code executes
before the user makes a selection.

However, if your select is inside a form, then when the user submits the
form, the selection will be in params[], and it can be accessed like
this: params[:name_of_select]. If you don’t know what the value of the
select’s name attribute is, do a ‘View Source’ when the select appears
in your browser, and look at the name attribute.

You can also use javascript to get the value of the select, but you need
to know javascript/jquery to do that, and based on your question, I’m
guessing you don’t know either.

Or, are you asking what choice will be pre-selected? The docs say this:

collection_select(object, method, collection, value_method, text_method,
options = {}, html_options = {})

Returns and tags for the collection of existing return
values of method for object‘s class. The value returned from calling
method on the instance object will be selected.

3

It’s a form. Has a drop-down menu, created by a collection_select. Since
it’s an edit page, then the value is ALREADY SELECTED by the time you
get to that edit page.

4

That default value is set by the model, through the controller, when
the view is rendered.

At what level do you need to get the value? (Because, as 7stud
pointed out, it’s already known to the system.) If you need to get the
value in a JavaScript within the page, you can either use rjs to set
the variable value, or you can use regular JS to read the current
value out of the form element.

val = $F(‘your_element_id’); //prototype JS

Walter

5

On Thu, Aug 25, 2011 at 5:26 AM, Leonel . [email protected]
wrote:

I have an edit form and I need to get the SELECTED VALUE from a
collection_select in a variable.

So if I have this…

<%= f.collection_select :part_id, @parts, :id, :cost_and_name, :prompt
=> “Select” %>

How can I peek inside and get, for example, the part_id?

the value selected when the page is rendered will be equal to
f.object.part_id

For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.

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