Rails：如何检查列是否有值？ [英] Rails: How do I check if a column has a value?

问题描述

如何完成此操作？

 <％for agent in @ broker.agents％> 
 ... 
<％if agent.cell％>< span class =cell-number>单元格：<％= agent.cell％>< / span> <％end％> 
 ... 
<％end％> 
  

我想测试代理是否有单元格号，如果是，条件。我目前似乎没有工作;

解决方案

这是您要求的：

 <％for agent in @ broker.agents％> 
<％unless agent.cell.blank？ ％> 
< span class =cell-number>单元格：<％= agent.cell％>< / span> 
<％end％> 
<％end％> 
  

单元格？方法的作用是单元格是nil还是空字符串。 Rails为所有ActiveRecord属性添加类似的函数。这将看起来更好一些：

 <％for agent in @ broker.agents％> 
< span class =cell-number> 
单元格：<％= agent.cell？ ？ none given：agent.cell％> 
< / span> 
<％end％> 
  

问号和冒号形成快速的if？then：else语句。在上面的代码中有两个问号，因为一个是方法名单元格的一部分？另一个是if / then / else结构的一部分。

How can I accomplish this?

<% for agent in @broker.agents %>
  ...
  <% if agent.cell %><span class="cell-number">Cell: <%= agent.cell %></span><% end %>
  ...
<% end %>

I want to test to see if the agent has a cell number, and if so, display what's inside the conditional. What I have currently doesn't seem to work; it just displays "Cell: ".

Thoughts?

解决方案

This is what you asked for:

<% for agent in @broker.agents %>
  <% unless agent.cell.blank? %>
    <span class="cell-number">Cell: <%= agent.cell %></span>
  <% end %>
<% end %>

The cell? method works whether cell is nil or an empty string. Rails adds similar functions for all ActiveRecord attributes. This will look a little nicer:

<% for agent in @broker.agents %>
  <span class="cell-number">
    Cell: <%= agent.cell? ? "none given" : agent.cell %>
  </span>
<% end %>

The question mark and colon form a quick "if ? then : else" statement. There are two question marks in the code above because one is part of the method name cell? and the other is a part of the if/then/else construction.

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