[jQuery] Basic custom Plugin not working

[morraine]

Hi guys i have tried to create my first plugin but its giving me some
odd behaviour.

what im trying to achieve is to put default text in an empty input
field and hide it when the field has focus and then show it again if
nothing was entered into the field on blur. This i have done pretty
easy but the problem start when i use the plugin on more than one
input filed per page and it treats all field like the last one in the
sequence. so if i focus the first field the text in the last filed in
the sequence will disappear ?!?!

This is my code for this simple plugin
Can anyone see the glaring mistake that i must have made????

function($){
   jQuery.fn.showhideinput = function(options) {

      var defaults = {
         text: "dd/mm/yyyy"
        };
      var options = $.extend(defaults, options);
      return this.each(function(index) {
            obj = $(this);
         objid = '#'+obj.attr('id');
         var inputtext = obj.val();
         if (inputtext == ''){
            obj.val(options.text);
            inputtext = options.text;
         }
         obj.focus(function () {
            //alert(objid + ' focus');
            if (obj.val() == inputtext){
               $(objid).val('');
            }
         });
         obj.blur(function () {
            //alert(objid + ' blur');
            if (obj.val() == ''){
               $(objid).val(inputtext);
            }
         });
      });
   };
})(jQuery);