ROR汇集---will_paginate

转自：http://github.com/mislav/will_paginate/tree/master

WillPaginate

Pagination is just limiting the number of records displayed. Why should you let it get in your way while developing, then? This plugin makes magic happen. Did you ever want to be able to do just this on a model:

  Post.paginate :page => 1, :order => 'created_at DESC' 

… and then render the page links with a single view helper? Well, now you can.

Some resources to get you started:

• Installation instructions on the wiki
• Your mind reels with questions? Join our Google group.
• How to report bugs

Example usage

Use a paginate finder in the controller:

  @posts = Post.paginate_by_board_id @board.id, :page => params[:page], :order => 'updated_at DESC'
 

Yeah, paginate works just like find — it just doesn’t fetch all the records. Don’t forget to tell it which page you want, or it will complain! Read more on WillPaginate::Finder::ClassMethods.

Render the posts in your view like you would normally do. When you need to render pagination, just stick this in:

  <%= will_paginate @posts %>
 

You’re done. (You can find the option list at WillPaginate::ViewHelpers.)

How does it know how much items to fetch per page? It asks your model by calling its per_page class method. You can define it like this:

class Post < ActiveRecord::Base cattr_reader :per_page @@per_page = 50 end
… or like this: 
class Post < ActiveRecord::Base def self.per_page 50 end end

… or don’t worry about it at all. WillPaginate defines it to be 30 by default. But you can always specify the count explicitly when calling paginate:

@posts = Post.paginate :page => params[:page], :per_page => 50
 

The paginate finder wraps the original finder and returns your resultset that now has some new properties. You can use the collection as you would with any ActiveRecord resultset. WillPaginate view helpers also need that object to be able to render pagination:

  <ol>
    <% for post in @posts -%>
      <li>Render `post` in some nice way.</li>
    <% end -%>
  </ol>

  <p>Now let's render us some pagination!</p>
  <%= will_paginate @posts %>
 

More detailed documentation:

• WillPaginate::Finder::ClassMethods for pagination on your models;
• WillPaginate::ViewHelpers for your views.

Authors and credits

Authors:	Mislav Marohnić, PJ Hyett
Original announcement:	errtheblog.com/post/929
Original PHP source:	www.strangerstudios.com/sandbox/pagination/diggstyle.php

 

 

All these people helped making will_paginate what it is now with their code contributions or just simply awesome ideas:

Chris Wanstrath, Dr. Nic Williams, K. Adam Christensen, Mike Garey, Bence Golda, Matt Aimonetti, Charles Brian Quinn, Desi McAdam, James Coglan, Matijs van Zuijlen, Maria, Brendan Ribera, Todd Willey, Bryan Helmkamp, Jan Berkel, Lourens Naudé, Rick Olson, Russell Norris, Piotr Usewicz, Chris Eppstein, Denis Barushev, Ben Pickles.

Usable pagination in the UI

There are some CSS styles to get you started in the "examples/" directory. They are showcased online here.

More reading about pagination as design pattern:

• Pagination 101
• Pagination gallery
• Pagination on Yahoo Design Pattern Library

Want to discuss, request features, ask questions? Join the Google group.

 

建议：

1、如果项目对分页的参数大多数要求一致的话。分页参数可以写进yml文件。

2、分页可以先查找，再调用paginate插件。如：

posts = Post.find(:all) #you can define your complex query here. @posts = posts.paginate :page => params[:page], :per_page => 50, :order => 'updated_at DESC'