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[英]Rails 5: How to order models by associated model attribute, and make them distinct
[英]How to look up associated models by an attribute hash
僅供參考,該項目使用Mongo / Mongoid
可以說我有模型A,B,C和D。A has_many Bs has_many Cs has_many Ds。
每個屬性都有一個“名稱”屬性,該屬性在其關聯樹中是唯一的,但不一定在整個模型類中都是如此。
如果我有這樣的哈希:
{a: "name1", b: "name2", c: "name3"}
要么
{a: "name2", b: "name2", c: "name3", d: "name4"}
如何在哈希中找到最后一個模型? 本質上(盡管散列大小需要動態變化):
@item = A.where(name: "name1").first
.Bs.where(name: "name2").first
.Cs.where(name: "name3").first
你可以做
@item = A.where(name: "name1").first
@item = @item ? @item.Bs.where(name: "name2").first : Bs.where(name: "name2").first
@item = @item ? @item.Cs.where(name: "name3").first : Cs.where(name: "name3").first
@item = @item ? @item.Ds.where(name: "name4").first : Ds.where(name: "name4").first
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