Block in views, concat, capture, content_for,yield,content_tag

rails 2.2 block in view
block in view before
<br /># 2.2 之前, 叫concat 時都要, 叫block.binding<br /># 2.2 之後就不用囉<br />=begin<br />用這樣就可以不用在view 裡面做一堆 <% if admin 的動作 %><br />也可以把view content 不同的部份當成 variable 來用帶入相同的外圍, DRY<br />=end<br />#version rails 2.0.2<br />def admin_area(&block)<br /> if admin?<br /> concat content_tag(:div, capture(&block), :class => 'admin'), block.binding<br /> end<br />end<br /><br />#version rails 2.2<br />def admin_area(&block)<br /> if admin?<br /> concat content_tag(:div, capture(&block), :class => 'admin')<br /> end<br />end<br />
concat source code<br />#actionpack-2.0.2/lib/action_view/helpers/text_helper.rb<br /> def concat(string, binding)<br /> eval(ActionView::Base.erb_variable, binding) << string<br /> end<br /><br />#actionpack-2.2.2/lib/action_view/helpers/text_helper.rb<br /> def concat(string, unused_binding = nil)<br /> if unused_binding<br /> ActiveSupport::Deprecation.warn("The binding argument of #concat is no longer needed. Please remove it from your views and helpers.", caller)<br /> end<br /><br /> output_buffer << string<br /> end<br />

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其他學到的 concat, capture, yield,content_tag

concat <br /> # The preferred method of outputting text in your views is to use the<br /> # <%= "text" %> eRuby syntax. The regular _puts_ and _print_ methods<br /> # do not operate as expected in an eRuby code block. If you absolutely must<br /> # output text within a non-output code block (i.e., <% %>), you can use the concat method.<br /> <br />你不想在外面的view, 弄一堆 <% %> 的 tag<br />可以選擇用一個大的包起來, 然後用concat 把需要呈現在view 的地方印出來<br />
capture<br />#The capture method allows you to extract part of a template into a variable. You can then use this variable anywhere in your templates or layout.<br /><br />#可以讓你把把view 存起來當變數, 做一些判斷<br />#在上面block in view 的作用就是這樣 先存起來讓concat 去用<br />#如果是用yield 就會直接出去在view了<br />#views/list.rhtml<br /><% @header = capture do %><br /> <%= link_to "#{@user.name}的早起紀錄", home_url, :class => 'ebhead'%><br /><% end %><br /><br />#layout.rhtml<br /> <% if @header %><br /> <h1 class="ebhead"><br /> #OOXX<br /> <%= @header %><br /> #OOXX<br /> </h1><br /> <% else %><br /> <h1 class="ebhead"><br /> #OOXX<br /> <%= @header %><br /> #OOXX<br /> </h1><br /> <% end %><br />
yield, content_for<br />#yield 最常用的到當然就是在layout 叫content<br /><br /> <%= yield %><br /><br />#再來就是利用content_for 把 部份的 view 存成block<br /><br />#layouts/application.html.erb<br /><br />(head)<br /> <%= yield :head_specific %><br />(/head)<br />#views/show.html.erb<br /><br /> <% content_for :head_specific do %><br /> #可以根據不同的頁面去放不同的東西例如include 不同的css<br /> #然後等 yield, 這邊就是會在layout 裡 head tag 裡面放入 <br /> [%= stylesheet_link_tag "main" %]<br /> [%= javascript_include_tag "spotlight" %]<br /> <% end %><br />
content_tag<br />=begin<br />Returns an HTML block tag of type name surrounding the content. Add HTML attributes by<br /> passing an attributes hash to options. Instead of passing the content as an argument, you <br />can also use a block in which case, you pass your options as the second parameter. Set <br />escape to false to disable attribute value escaping.<br /><br />完全就是很high 的讓你不用寫html 包來包去<br />尤其是在上面用concat 的地方 不用 concat '<div>' ... concat '</div>'<br />=end<br /> content_tag(:p, "Hello world!")<br /> # => <p>Hello world!</p><br /> content_tag(:div, content_tag(:p, "Hello world!"), :class => "strong")<br /> # => <div class="strong"><p>Hello world!</p></div><br /> content_tag("select", options, :multiple => true)<br /> # => <select multiple="multiple">...options...</select><br /><br /> <% content_tag :div, :class => "strong" do -%><br /> Hello world!<br /> <% end -%><br /> # => <div class="strong">Hello world!</div><br />