how to set selected value in <%= f.select_tag %> dropdown list, how? - forms

Question

i have a long list dropdown menu including all currencies, i want the last selected value to be the default selected value in the list.
i am using Rails 4.0.0 and ruby 2.0.0
i am not using a model, i am just using a controller. i have put the dropdown list options inside a helper.
form.html.erb
<div class="calculator">
<%= form_for :convertor, :url => {:controller => "converter", :action => "show" } do |f| %>
<%= f.label :from_currency %>
<%= f.select :from_currency, options_for_select(currencies, :selected => params[:from_currency]) %>
<%= f.text_field :amount, :placeholder => "Amount", id: "textfield" %>
<%= #amount %>
<br>
<%= f.label :to_currency %>
<%= f.select :to_currency, options_for_select(currencies, :selected => params[:to_currency].to_i ) %>
<%= #result %>
<br>
<%= f.submit "Calculate", class: "btn btn-large btn-primary", id: "submitButton" %>
<% end %>
</div>
the list options are loaded from a helper *<%= f.select :to_currency, options_for_select(currencies, :selected => params[:to_currency].to_i ) %>* with name currencies
the dropdown list, in a helper
def currencies
[
['United Arab Emirates Dirham (AED)', 'AED'],
['Netherlands Antillean Guilder (ANG)', 'ANG'],
['Argentine Peso (ARS)', 'ARS'],
['Australian Dollar (A$)', 'AUD'],
['Bangladeshi Taka (BDT)', 'BDT'],
['Bulgarian Lev (BGN)', 'BGN'],
['Bahraini Dinar (BHD)', 'BHD'],
]
end
what am i doing wrong here?

Answer 1

A couple of things:
options_for_select takes two arguments: the list of options and the value that you want selected.
You're passing through the value as a hash: :selected => params...
The parameter name is wrong.
In your controller, you're saying that the parameter is called this:
params[:convertor][:from_currency]
But in your view, you have params[:from_currency].
Therefore, the solution to this is to do this:
<%= f.select :from_currency, options_for_select(currencies, params[:convertor][:from_currency]) %>

Answer 2

This code works for me.
in application helper
module ApplicationHelper
def opts_for_select_cur
opts_for_select = [
['United Arab Emirates Dirham (AED)', 'AED'],
['Netherlands Antillean Guilder (ANG)', 'ANG'],
['Argentine Peso (ARS)', 'ARS'],
['Australian Dollar (A$)', 'AUD'],
['Bangladeshi Taka (BDT)', 'BDT'],
['Bulgarian Lev (BGN)', 'BGN'],
['Bahraini Dinar (BHD)', 'BHD'],
]
return opts_for_select
end
end
and in view
<script type="text/javascript">
$(document).ready(function(){
$('#st').change(function(){
var inputText = $('#st :selected').val();
$("#hidden_one").val(inputText);
$("a").attr("href", "?value="+inputText );
});
$('#aa').click(function(){
var inputText = $('#st :selected').val();
$("a").attr("href", "?value="+inputText );
});
});
<%= f.select :text, options_for_select(opts_for_select_cur, params[:value]), {}, { id: "st" } %>
<br>
<%= link_to "refresh",nil, id: "aa" %>
the result is a select box with selected value.

Answer 3

this can help
<%= f.label :from_currency %>
<% if #from_cur.present? %>
<%= f.select :from_currency, options_for_select(currencies, #from_cur) %>
<% else %>
<%= f.select :from_currency, options_for_select(currencies), :required => true %>
<% end %>
<%= f.text_field :amount, :placeholder => "Amount", :required => true, id: "textfield" %>
<br>
<%= f.label :to_currency %>
<% if #from_cur.present? %>
<%= f.select :to_currency, options_for_select(currencies, #to_cur), :required => true %>
<% else %>
<%= f.select :to_currency, options_for_select(currencies), :required => true %>
<% end %>
i appreciate.