Activerecord memo (2)

Find的參數
1.select
<br />#select 可以只選出我們想要的<br />f = Forum.find(:all, :joins => :user, :select => "forums.*, users.name")<br />#如果參數是設成 :select => "*" 那麼users全部的attributes 也會被select 進去<br />>> f[0].attributes<br />=> {"name"=>"iflakela", "last_comment_time"=>Sat Aug 23 19:34:17 +0800 2008, "public"=>nil, "subject"=>"111111111", "id"=>6, "group_id"=>1, "content"=>"11111111", "user_id"=>1, "comments_count"=>2, "created_at"=>Sat Aug 23 19:19:02 +0800 2008}<br /><br />>> f[0].attribute_names<br />=> ["comments_count", "content", "created_at", "group_id", "id", "last_comment_time", "name", "public", "subject", "user_id"]<br /><br />#判斷有沒有這個attribute<br />>> f[0].attribute_present?("lala")<br />=> fales<br />
2.group
<br /> Forum.find(:all, :group => 'DATE(created_at)', :select => "subject, DATE(created_at)")<br /> SELECT subject, DATE(created_at) at FROM `forums` GROUP BY DATE(created_at);<br />+--------------------------+-----------------+<br />| subject | DATE(created_at) |<br />+--------------------------+-----------------+<br />| 111111111 | 2008-08-23 |<br />| cc | 2008-08-27 |<br />| aaaaaaaaaaaaa | 2008-08-29 |<br />| a | 2008-09-03 |<br />| dddddddd | 2008-12-07 |<br />| 333333333333 | 2008-12-13 |<br />| 1111111 | 2008-12-14 |<br />| lalalal | 2008-12-28 |<br />
統計的method
有average, maximum, minimum, sum, count
1. count, group
<br />#每天forum 的數目<br />>> Forum.count(:all, :group => 'DATE(created_at)')<br />=> [["2008-08-23", 6], ["2008-08-27", 1], ["2008-08-29", 1], ["2008-09-03", 1], ["2008-12-07", 3], ["2008-12-13", 2], ["2008-12-14", 3], ["2008-12-28", 3], ["2009-01-03", 2], ["2009-01-08", 1]]<br />
2. maximum
<br /> Status.maximum :score, :group => "user_id", :limit => 3, :order => "max(score) desc"<br />=> [[2, 3], [4, 3], [6, 2]]<br />SELECT max(`statuses`.score) AS max_score, user_id FROM `statuses` GROUP BY user_id ORDER BY max(score) desc LIMIT 3;<br />+-----------+---------+<br />| max_score | user_id |<br />+-----------+---------+<br />| 3 | 2 | <br />| 3 | 4 | <br />| 2 | 6 | <br />+-----------+---------+<br /><br />
memo: find_by_sql, count_by_sql
<br />u = User.find_by_sql("select * from forums, users where forums.user_id=users.id")<br /><br />count = LineItem.count_by_sql("select count(*) " +<br /> " from line_items, orders " +<br /> " where line_items.order_id = orders.id " +<br /> " and orders.name = 'Dave Thomas' " )<br />
find_or_initialize_by, find_or_create_by

strain, 寫成這樣好醜 XD

        if params[:type]
          SmsRecord.sys
        else
          SmsRecord.purchase
        end.find(:all, :conditions => cond).each do |row|
          csv << [row.id, row.sms_purchase_record_id, row.user_id, row.send_to_sms_at.strftime('%Y/%m/%d %H:%M'), row.sms_rsp_code]
        end
       

jquery each find what is different

[html]
<div id="'test'">
 <span id="'each'">(click here to change)</span>
 <ul>
   <li class="cc">Eat</li>
   <li class="cc">Sleep</li>
   <li class="bb">Be merry</li>
 </ul>
</div>

[script 1]
    $("#test span").click(function () {
          if ($("#test").find('li')) {
          alert($(this).html());
        }
      });
$(this) is $(#test span)
[script 2]
    $("#test span").click(function () {
          if ($("#test li")) {
          alert($(this).html());
        }
      });

$(this) is $(#test span)


[script 3]
      $("#test span").click(function () {
        $("#test li").each(function(i, e){
          alert($(this).html());
        }
      });

$(this) is really every li tag
i is the iterator counter
e == $(this)


Returning 'false' from within the each function completely stops the loop through all of the elements (this is like using a 'break' with a normal loop). Returning 'true' from within the loop skips to the next iteration (this is like using a 'continue' with a normal loop).

filter, find

http://manalang.com/jquery/docs/index.html#filter-expr
http://www.learningjquery.com/2008/08/quick-tip-dynamically-add-an-icon-for-external-links

      $(document).ready(function() {
        $('#extlinks a').filter(function() {
          return this.hostname && this.hostname !== location.hostname;
        }).after(' <img src="/images/external.png" alt="external link">');
      });

filter 可以塞function來parse, return true 才會跑後面的after

jQuery tutorial, find and filter

http://www.learningjquery.com/2006/11/how-to-get-anything-you-want-part-1
http://www.learningjquery.com/2006/12/how-to-get-anything-you-want-part-2

filter will select a certain subset (zero or more) of the already 
selected elements.
find will select a set of (zero or more) elements that are descendants 
of the already selected elements.
Here is an example:
$('div').filter('.elephants'); // <-- selects the second div, because   it has class="elephants" 
$('div').find('.elephants'); // <-- selects the first paragraph,   because it has class="elephants" 
* Note that these two examples are very simple and would probably be 
better written as ...
$('div.elephants');
  ... and ...
$('div .elephants');



$('li + li > a[@href$=pdf]') gets all links ending in
“pdf” that are children of any list item that has another list item as
its previous sibling. It won’t get the first list item’s silly.pdf
because that list item has no other list items before it.

$('span:hidden') gets any span element that is hidden.

$('li:even') gets all odd-numbered list items (because, in javascript, numbering starts with 0, not 1).

$('li:lt(3)') gets the first 3 list items. “lt” stands for “less than,” and it starts counting at 0, not 1.

$('li:not(.goofy)') gets list items 1, 2, and 4, because they’re not “goofy.”
$('p a[@href*=#]') gets any links that are inside a paragraph and have an “href” attribute starting with “#” — containing “#” anywhere. in other words, same-page links. There are problems with trying to identify same-page links this way. I’ll write about this in an upcoming entry. Note the space between the “p” and the “a”; that means that the “a” is a descendant of the “p.”

find random offset

http://blog.pbg4.org/2008/1/2/find-randomly-redux
http://wiki.rubyonrails.org/rails/pages/HowtoSelectRandomRecords
http://groups.google.com/group/Ruby-on-Rails-Taiwan/browse_thread/thread/27ec511fa258ca08
http://blog.commonthread.com/2007/12/7/tip-ruby-on-rails-random-array-element

目前一般的最佳解是這個, random 出offest
def self.find(*args)
scope = args.first
if scope.to_s == "random"
  super :first, :offset => (rand count).to_i
elsif scope.to_s == "public"
  # blah, blah...
else
  super
end
end
ps:console下
Record.find(:first, :offset => (rand Record.count).to_i)

要用Record.count, sometimes some record would be deleted
ps2:bad way find(rand(count) + 1) rescue ActiveRecord::RecordNotFound random

find, all, first

find(:all) 找不到是 []
find(:first) 找不到是 nil