Ruby-on-rails rails 3.0.3 检查布尔值是否为真
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rails 3.0.3 check if boolean value is true
提问by andkjaer
I want to check if a value is true or false.
我想检查一个值是真还是假。
<% if item.active? %>
<%= image_tag('on.png', :alt => "Active", :border => 0) %>
<% else %>
<%= image_tag('off.png', :alt => "Inactive", :border => 0) %>
<% end %>
That doesn't work, but this works?
那行不通，但这行得通吗？
<% if item.active == true %>
<%= image_tag('on.png', :alt => "Active", :border => 0) %>
<% else %>
<%= image_tag('off.png', :alt => "Inactive", :border => 0) %>
<% end %>
Shouldn't the first method work or am I missing something?
第一种方法不应该起作用还是我错过了什么？
回答by nonopolarity
if this line works:
如果这条线有效：
if item.active == true
then
然后
if item.active
will also work. if item.active?works only if there is a method whose name is actually active?, which is usually the convention for naming a method that returns true or false.
也会起作用。 if item.active?仅当存在名称实际上为 的方法时才有效active?，这通常是命名返回 true 或 false 的方法的约定。
回答by rwilliams
This should work for you assuming item.activeis truly a boolean value. Unless there is a method defined for item.active?your example will only return a no-method error.
假设item.active它确实是一个布尔值，这应该对你有用。除非为item.active?您的示例定义了方法，否则只会返回无方法错误。
<% if item.active %>
<%= image_tag('on.png', :alt => "Active", :border => 0) %>
<% else %>
<%= image_tag('off.png', :alt => "Inactive", :border => 0) %>
<% end %>
回答by gsumk
The other way is using single line if else
另一种方法是使用单行 if else
<%= active ? here is your statement for true : here is your statement for false %>
For active?to work there should be an def active?method in your item object.
为了active?工作def active?，您的项目对象中应该有一个方法。
