我尝试了笔记。 我如何这样做? 感谢阅读。
如果你想知道@note是否有任何关联tags,你可以使用
@note.tags.empty?
在增补中,你可以考虑为塔格斯设立一个反切栏。 随附<代码>:标签_count,你将不需要再问。 然后,请上@note.tags_count= 0,@note.tags_count.zero? 或你喜欢什么。
如果存在任何标签,请打电话@note.tags.any?。 请注意,这将打到数据库做计数。 您在退出@note时可能要加入,以挽救这一疑虑。 例如:
Note.first(:select => notes.*, case when tags.id is not null then 1 else 0 end as has_any_tags , :joins => "LEFT JOIN tags ON tags.note_id = notes.id")
页: 1 如果存在任何相关的标签,即为<代码>0(false)或1(true)。
您可将上述询问选项移至缺省范围,并将实地情况总结为出人:
class Note
has_many :tags
default_scope :select => notes.*, case when tags.id is not null then 1 else 0 end as has_any_tags , :joins => "LEFT JOIN tags ON tags.note_id = notes.id"
def has_any_tags?
has_any_tags == "1"
end
end
现在,这一切都是透明地发生的:
>> Note.first.has_any_tags?
=> true
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