Rails has_many :through 居然不能识别变形复数
发现一个很 2b 的问题。
Rails 官网给 has_many :through 举的例子如下：
class Physician < ApplicationRecord
has_many :appointments
has_many :patients, through: :appointments
end
class Appointment < ApplicationRecord
belongs_to :physician
belongs_to :patient
end
class Patient < ApplicationRecord
has_many :appointments
has_many :physicians, through: :appointments
end
如果把 model 名字改成单复数需要变形的单词就报错了，必须加上 source 指明 model 原单数名称，比如：
class Person < ApplicationRecord
has_many :bars
has_many :foos, through: :bars
end
class Bar < ApplicationRecord
belongs_to :person
belongs_to :foo
end
class Foo < ApplicationRecord
has_many :bars
has_many :people, through: :bars, source: 'person'
end
如果不加这个 source: 'person'，在查询 @foo.people 时就会报 ActiveRecord::HasManyThroughSourceAssociationNotFoundError 的错误
ShowLew
回复
可别一概而论，实际上 person 是有两种复数形式的。一般来说，当我们引述相对于“动物”或“东西”的“人”的概念，并为了概括一个不确定数量的群体时，用的是 people；而当引述特定数量范围的独立个体时，用的是 persons。通常 persons 多用于法律法规之类的地方，比如说法院指代犯罪嫌疑人等的时候（因为犯罪嫌疑人的数量总是确定的，你不能给可能存在或不存在的人定罪吧？）就会用 persons。
韦氏词典里有如下阐述，比我说的更专业一些：
Many usage guides over the years have suggested that there is a clear distinction between these two words; people is used when referring to a collective group or indeterminate number, and persons serves better when referring to individuals (or a number of individuals). There are many instances in which this difference may be observed, often when the two words are side by side.
