I have an association of has_many :through with tags, taggings and categories
Tags
has_many :taggings
has_many :categories, through: :taggings
Taggings
belongs_to :tag
belongs_to :category
Categories
has_many :taggings
has_many :categories, through: :taggings
When I try to query
tag = Tag.where("name LIKE ?", "#{query}")
tag.categories
there's an error:
Undefined categories
I don't know what the difference when you use find and where because when I used find it works fine. Can you give me the idea why?
where
returns an array that contains result. find
on the other hand returns an object. Try:
tag = Tag.where("name LIKE ?", "#{query}")
tag.first.categories
如果您只想要第一张唱片,使用起来会更简单,更优雅
Tag.find_by_name(query).categories
Find return an object and where clause returns the array of objects when you need to find one record by where clause then you should use:
tag = Tag.where("name LIKE ?", "#{query}").first
categories = tag.categories if tag
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