Updating quantity in Rails Form - ruby-on-rails-3

Question

I'm building a simple inventory app that keeps track of the quantity of an item.
In a basic form I would be updating item_quantity with whatever arbitrary number I type in.
But how would I create a form/code that would allow me to tag on +20 on top of the already existing item quantity?

Answer 1

You could do it with jquery/javascript
Something like:
In your view:
<%= f.text_field :item_quantity, :id => 'item_quanity' %>
+20
In javascript:
$(function() {
$('#increment_item_quantity').on('click', function(e) {
e.preventDefault();
var currentVal = parseInt($('#item_quantity').val());
$('#item_quantity').val(currentVal + 20);
});
});
You'd probably want to make sure the currentVal is a number (since parseInt('') => NaN)
And then submit as usual
Or
If you wanted to do this via a form:
In your view:
<%= form_for #item, incr_quantity_path(#item) do |f| %>
<%= f.submit %>
<% end %>
Then in your controller:
def incr_quantity
#item = Item.find(params[:id])
# I'd probably move the increment logic into the model
#item.quantity += 20
#item.save
# respond to it however you want
end
Or if you want to increment the value by what's entered:
Model:
class Item < AR::Base
...
attr_accessible :incr_quantity_by
def increment_quantity_by
quantity += incr_quantity_by
end
...
end
View:
<%= form_for #item, incr_quantity_path(#item) do |f| %>
<%= f.text_field :incr_quantity_by
<%= f.submit %>
<% end %>
Controller:
def incr_quantity
#item = Item.find(params[:id])
#item.increment_quantity_by
#item.save
# respond to how you want
end