Hello everyone,
I want to add a few columns in the directory items model. ( ‘Solutions’ and ‘Points’ )
I was able to modify the code for the model and templates directly, but how can I achieve this via a plugin ?
If not possible via plugin, is it possible to use my own github repo ( with these changes ) instead but somehow continue to get updates from Discourse repo.
Thanks
I’m Not able to understand the exact usecase but definitely adding some columns can be achieved via plugins!
You may start writing a plugin using the official Guidelines and Then use it in order to ensure You get official updates.
Here is Some Help:
Hey @itsbhanusharma, thanks for the link.
I’ve gone through the Beginner’s Guide, but couldn’t find DB modifications in it.
You’ve any plugin in mind which does something similar ?
Have You gone through the whole series?
I’d have a look in the Plugin repo to find if there is something.
EDIT: have a Look Here maybe this Helps!
FWIW I’ve decided to go this route with a plugin of mine, where PluginStoreRow and CustomFields didn’t qqquite cut it on their own. 
Caveat emptor You should be trying really hard not to do this - It’s not recommended behaviour to modify the database from within a plugin, but it can be done unobtrusively in small, additive doses (I’d say you never for any reason want to remove or change existing columns)
Here’s how I did it:
# plugins/my_plugin/migrations/add_column.rb
class AddColumn < ActiveRecord::Migration[5.1]
def change
add_column :post_custom_fields, :my_column, :jsonb, default: {}, index: true
end
end
NB: it’s a good idea to namespace your column with the name of your plugin, since adding a column with a generic name like ‘value’ could end up actually existing in the future and then you’d have a real problem.
# plugin.rb
if !PostCustomField.new.respond_to?(:my_column)
require Rails.root.join('plugins', 'my_plugin', 'migrations', 'add_column')
AddColumns.new.up # <-- this runs the migration
end
rails s or rails c after this, you should see the following:add_column(:post_custom_fields, :my_column, :jsonb, {:default=>{}, :index=>true})
that means it worked! Subsequent boots of the app shouldn’t display this message.
# plugins/my_plugin/tasks/remove_column.rake
# (I think there's a better way to do this, but this line works.)
# Essentially, we need the environment loaded so that ActionRecord::Migration is defined.
require File.expand_path(File.dirname(__FILE__) + '../../../config/environment'
desc "remove my_column from the database"
task "my_column:remove" do
require Rails.root.join('plugins', 'my_plugin', 'migrations', 'add_column')
AddColumn.new.down
end
Then, in your README, instructions on how to use it
This plugin adds a column to the database. If you want to remove this plugin and don't plan on using it again, perform the following steps:
- Enter your discourse container
./launcher enter app
- Run the following command to reverse the database changes
bundle exec rake -f plugins/my_plugin/tasks/remove_column.rake -T
- Remove the 'git clone' line from your app.yml
- Rebuild your container
./launcher rebuild app
Note that dropping this column is permanent and irreversible for the data stored there..
As always, let me know if I’ve missed something or if this can be improved.
我在 Rails Active Record 文档中找不到这种直接调用 up 方法的示例。
AddColumns.new.up
通常迁移是通过 rake db:migrate 命令执行的，而不是直接用 Ruby 调用。因此，我认为更好的做法是在插件中设置一个 migrate 目录，然后在 plugin.rb 文件中创建指向 /discourse/db/migrate 目录的符号链接。这样，Rails 的迁移基础设施（包括回滚功能）也可以被插件使用。或许可以在插件的 README 中添加关于如何回滚特定变更的文档说明。看起来可以通过类似以下方式回滚特定的迁移：
rake db:migrate:down VERSION=20100905201547
https://stackoverflow.com/questions/3647685/how-to-rollback-a-specific-migration
我很希望能听到大家对这一点的看法。另外，我认为仅仅链接到自定义字段（custom fields）并不够高效。我打算使用 Discourse 创建一个中英词典，仅依赖自定义字段无法满足我的需求。
我为插件创建了一个迁移和模型生成器：GitHub - spirobel/discourse at plugin_model_and_migrations · GitHub
我认为像这里展示的那样处理插件迁移的方式并不是一个好主意。