rails if对象位于数组中

I need to check, if for each item in @line_items if it is in different array say @quote_items

我需要检查@line_items中的每个条目，如果它在不同的数组中，比如@quote_items

Controller:

控制器:

def index
  @line_items = LineItem.all
  @quote_items = QuoteItem.all
end

View:

观点:

<% for line_item in @line_items %>
   <% if @quote_items.include?(line_item) %>
     line_item in quote item! 
   <% else %>
     line_item NOT in quote item! 
   <% end %>
...
<% end %>

Is there an easy way to do this? include? doesn't seem to work the way I want. Seems to just yield false for me all the the time.

有简单的方法吗?包括什么?似乎不像我想的那样。对我来说似乎一直都是假的。

3 个解决方案

#1

You are right it will always return false because you are trying to check if the array of @quote_items has a line item object

您是正确的，它总是返回false，因为您试图检查@quote_items数组是否有一个行项对象。

@quote_items.include?(line_item)

which obviously will always be false because your @quote_items instance is an array of QuoteItem objects and @line_items instance is an array of LineItem object. So they are always different objects.

因为@quote_items实例是QuoteItem对象的数组，@line_items实例是LineItem对象的数组。所以它们总是不同的物体。

I think in this situation you may want to compare some common attribute of quote_item and line_item. For example if you want to compare name attribute then

我认为在这种情况下，您可能需要比较quote_item和line_item的一些常见属性。例如，如果您想比较name属性

quote_item_names = @quote_items.map(&:name)

and then

然后

<% if quote_item_names.include?(line_item.name) %>
 line_item in quote item! 
<% else %>
 line_item NOT in quote item! 
<% end %>

#2

Like it was pointed out in discussion above — it depends on which criterion you're comparing objects in 2 arrays.

正如上面的讨论所指出的那样——这取决于您在两个数组中比较对象的标准。

If objects are of the same class (or the same ancestor), then include? will work.
如果对象属于相同的类(或相同的祖先)，则包含?将工作。
If objects are different, and you only want to compare their ids (although this makes little sense), it'd be something like this:

如果对象是不同的，并且您只想比较它们的id(尽管这没有什么意义)，它应该是这样的:
```
line_item_ids = @line_items.map(&:id) # array of just the attribute we need
@quote_items.each do |quote_item|
  if line_item_ids.include?(quote_item.id)
    # line item with the same id found
  else
    # ...
  end
end
```
You can do the above with any attribute, not just id.

您可以使用任何属性来完成上面的操作，而不仅仅是id。
If in both cases your objects are plain strings or symbols, make sure you're converting everything to string or symbol. Sometimes I forget and comparisons end up being false.

如果在这两种情况下，对象都是普通的字符串或符号，请确保将所有内容转换为字符串或符号。有时我忘记了，而比较最终是错误的。

#3

@line_items & @quote_items should return an array that includes the common items between them. @line_items - @quote_items return items that are in @line_items but not in @quote_items.Your code should work though, are you sure there are common items between them? Note that item equality is checked by the == operator, so you might need to provide that for your item class.

@line_items & @quote_items应该返回一个包含它们之间公共项的数组。@line_items - @quote_items返回@line_items中但不在@quote_items中的项。但是您的代码应该可以工作，您确定它们之间有公共项吗?注意，==运算符检查了项的相等性，因此您可能需要为您的item类提供这个值。

#1