Rails：基于来自另一个阵列的记录（字符串）查询数组

Question

每个用户有许多SaleItems和许多NeededItems。我想查询用户1的SaleItem名字，看看其中是否也有类似的名字，以用户2的NeededItems（“名”是唯一的属性）

@needed_item_of_user2 = NeededItem.where("user_id = ?", 2).first 
# "Pikachu Pokemon card" 
@sale_items_of_user1 = SaleItem.where("user_id = ?", 1) 
# "Baseball cards", "Water Heater", "Pikachu doll", "Squirtle Pokemon card" 
@matching_sale_items = @[email protected]_item_of_user2.name 
# It should output either "Squirtle Pokemon card" (high accuracy) or 
# all except "Water Heater" (low accuracy) 

我应该使用什么方法来获得@matching_sale_items?精确的匹配

我已经试过：基于How do I search within an array of hashes by hash values in ruby?

和

@matching_sale_items = @sale_items_of_user1.select do |sale| 
    sale["name"] == @needed_item_of_user2.name 
end 

@matching_sale_items = @sale_items_of_user1.map do |a| 
    a.name.downcase 
end.grep(/#{@needed_item_of_user2.name.downcase[0,4]}/) 
# outputs strings 

将来，我想使用该方法来查询SaleItems表与NeedItems表的匹配。

Answer 1

你可以试着这样做：

user1 = User.find 1 
user2 = User.find 2 
needed_items_names = user2.needed_items.pluck(:name) 
matched_items = user1.sale_items.where(name: needed_items_names) 

文档阅读：

• http://guides.rubyonrails.org/active_record_querying.html#pluck
• http://guides.rubyonrails.org/active_record_querying.html#hash-conditions 2.3.3子集条件