ActiveRecord自定義屬性

如何將自定義屬性分配給ActiveRecord模型？例如，我可以通過查詢時做到這一點：ActiveRecord自定義屬性

select("(CASE WHEN wishlist_items.id IS null THEN 0 ELSE 1 END) AS is_wishlisted_by_me").

這增加了自定義is_wishlisted_by_me屬性。但是，如果我已經有一個AR模型的實例，我想做的事：

model.is_wishlisted_by_me = true

這個返回NoMethodError: undefined method

NoMethodError: undefined method `is_wishlisted_by_me=' for #<SIImage:0x007fc8c41c7ef8> 
    from /Users/Test/.rvm/gems/ruby-1.9.3-p327/gems/activemodel-3.2.13/lib/active_model/attribute_methods.rb:407:in `method_missing' 
    from /Users/Test/.rvm/gems/ruby-1.9.3-p327/gems/activerecord-3.2.13/lib/active_record/attribute_methods.rb:149:in `method_missing' 
    from (irb):8 
    from /Users/Test/.rvm/gems/ruby-1.9.3-p327/gems/railties-3.2.13/lib/rails/commands/console.rb:47:in `start' 
    from /Users/Test/.rvm/gems/ruby-1.9.3-p327/gems/railties-3.2.13/lib/rails/commands/console.rb:8:in `start' 
    from /Users/Test/.rvm/gems/ruby-1.9.3-p327/gems/railties-3.2.13/lib/rails/commands.rb:41:in `<top (required)>' 
    from script/rails:6:in `require' 
    from script/rails:6:in `<main>'

來源

2013-06-30 0xSina

'NoMethodError：未定義method'不足以..未定義方法名稱也需要知道..給出完整的錯誤堆棧。 –

@Priti更新了堆棧 – 0xSina

@ 0xSina你在哪裏寫這行？ model.is_wishlisted_by_me = true –

我認爲你可以這樣做，在定義attr_accessible您型號：

attr_accessible :user_count 

r = User.find_by_sql("select count(*) as user_count from users") 

puts r.first.user_count

如果哈希會爲你做，你可以嘗試

User.connection.select_all("select count(*) as user_count from users")

將返回散列的陣列等[{：USER_COUNT => 1}]

來源

2013-06-30 10:59:40 Henry

這是我做了什麼：

after_initialize do 
    self.is_wishlisted_by_me = nil unless @attributes.key?("is_wishlisted_by_me") 
end 

def is_wishlisted_by_me 
    @attributes["is_wishlisted_by_me"] 
end 

def is_wishlisted_by_me=(value) 
    @attributes["is_wishlisted_by_me"] = value 
end

來源

2014-10-28 12:50:05 Michael

ActiveRecord自定義屬性

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