cwy007

controller

if params[:status].present?
  @user_balance_logs = @user_balance_logs.where(status: params[:status])
end

view

div class="form-group col-sm-4">

cwy007

ref links

https://ruby-china.org/topics/23713 http://railscasts.com/episodes/88-dynamic-select-menus-revised https://api.rubyonrails.org/classes/ActionView/Helpers/FormOptionsHelper.html#method-i-grouped_collection_select

cwy007

Update years later: instead of a Rake task, for PostgreSQL I just use

rake db:drop db:create

and then

cat somefile.sql | psql name_of_database

Dumping is

cwy007

CASCADE specifies that when a referenced row is deleted, row(s) referencing it should be automatically deleted as well

Your add_foreign_key calls would look like:

add_foreign_key "projects", "companies", on_delete: :cascade
add_foreign_key "tasks", "projects", on_delete: :cascade
add_foreign_key "task_times", "tasks", on_delete: :cascade

cwy007

Operator: @>
Description: contains
Example: ARRAY[1,4,3] @> ARRAY[3,1]
Result: t (AKA true)

Membership.where('roles @> array[?]', %w[as_champion whatever])
Membership.where('roles @> array[:roles]', :roles => some_ruby_array_of_strings)

cwy007

Active Record enums

Declare an enum attribute where the values map to integers in the database, but can be queried by name.

class Conversation < ActiveRecord::Base
  enum status: [ :active, :archived ]
end
 
conversation.archived!
conversation.active? # =&gt; false

cwy007

Rails

In the last blogpost about hstore we showed how to enable particular extension. This time is different (maybe easier), because array is Postgres’ data type, not an extension so there’s no need to enable that, because it’s accessible out of the box!

Migration

In two previous articles (mentioned in the introduction of this article) we created Book model and appropriate SQL schema. Let’s stick to that and extend it a little bit:

cwy007

def event(description)
  puts "ALERT: #{description}" if yield
end

# 将当前文件夹加入到加载路径中
$: << File.expand_path(File.dirname(__FILE__))

# 1. load 后面的参数不是绝对路径时，load 方法会从 `$:` 中查找文件名为 `event.rb` 的文件
load 'events.rb'

cwy007

It occurs that config/deploy.rb has lock '3.1.0'.

It was enough to change it to '3.2.0' and now it's working.

ref links

https://stackoverflow.com/questions/23095881/capistrano-deployment-problems

cwy007

类似问题

Failure/Error: it { should have_many(:users) }
ActiveRecord::StatementInvalid:
PGError: ERROR:  relation "users" does not exist

   LINE 4:              WHERE a.attrelid = '"users"'::regclass
                                           ^
   :             SELECT a.attname, format_type(a.atttypid, a.atttypmod), d.adsrc, a.attnotnull
 FROM pg_attribute a LEFT JOIN pg_attrdef d