Rails select from database
有人可以解释吗？ ，来自ruby guides
1 | <%= collection_select(:person, :city_id, City.all, :id, :name) %> |
我有一个附件模型，我想在创建对象时使用组合框选择其版本，并且我还想要一个新的版本选项。
here what attachment has
1 2 3 4 5 6 7 8 | def change create_table :attachments do |t| t.string :filename t.attachment :file t.string :version t.text :description t.timestamps null: false end |
UPDATE:
1 | <%= f.collection_select( :version, Attachment.where.not(version: nil), :version, :version) %> |
它正在那样工作，但我不明白，
尝试执行此操作以避免
的
1 | collection_select(:f, :attachment_id, Attachment.where.not(version: nil), :id, :version) |
collection_select的工作原理说明：
1 2 3 4 5 6 7 8 9 10 11 12 13 | collection_select( :f, # field namespace :attachment_id, # field name # result of these two params will be: <select name="f[attachment_id]">... # then you should specify some collection or array of rows. # In your example it is: Attachment.where.not(version: nil) # Then, you should specify methods for generating options :id, # this is name of method that will be called for every row, result will be set as key :version # this is name of method that will be called for every row, result will be set as value ) |
有关详细信息，请参见此内容。
检查此线程接受的答案，以获取有关collection_select工作原理的解释：有人可以用清晰，简单的方式向我解释collection_select吗？
在此选择：
1 | <%= collection_select(:f, :attachment_id, Attachment.all, :id, :version) %> |
您显示已创建附件的所有版本，因此如果附件表为空，您将得到null