当引擎上的 运行 `rails generate` 时，如何修复 `undefined method `railtie_namespace' 错误
How can I fix `undefined method `railtie_namespace'` error when running `rails generate` on the engine
问题如下：
# 1) Create full engine `myengine` with Rails 4.2.10
rails _4.2.10_ plugin new myengine --full
# 2) Try to rails generate
$ bin/rails g
/usr/local/lib/ruby/gems/2.6.0/gems/railties-4.2.10/lib/rails/engine/commands.rb:17:in `<top (required)>':
undefined method `railtie_namespace' for nil:NilClass (NoMethodError)
当您对引擎目录进行 symlink 并通过 link 到达该目录时出现问题，如下所示：
cd path/to/somewhere
rails _4.2.10_ plugin new myengine --full
ln -s path/to/somewhere/myengine ~/favorite/myengine
cd ~/favorite/myengine
./bin/rails g
如果你这样做，你会 运行 进入错误。要解决此问题，请更改 bin/rails 顶部的一些行，如下所示：
# from
ENGINE_ROOT = File.expand_path('../..', __FILE__)
ENGINE_PATH = File.expand_path('../../lib/myengine/engine', __FILE__)
# to
require 'pathname'
ENGINE_ROOT = Pathname.new(__FILE__).realpath + '../..'
ENGINE_PATH = ENGINE_ROOT + 'lib/myengine/engine'
请参阅 ::Rails::Engine.find 的实施，了解补丁为何有效。
问题如下：
# 1) Create full engine `myengine` with Rails 4.2.10
rails _4.2.10_ plugin new myengine --full
# 2) Try to rails generate
$ bin/rails g
/usr/local/lib/ruby/gems/2.6.0/gems/railties-4.2.10/lib/rails/engine/commands.rb:17:in `<top (required)>':
undefined method `railtie_namespace' for nil:NilClass (NoMethodError)
当您对引擎目录进行 symlink 并通过 link 到达该目录时出现问题，如下所示：
cd path/to/somewhere
rails _4.2.10_ plugin new myengine --full
ln -s path/to/somewhere/myengine ~/favorite/myengine
cd ~/favorite/myengine
./bin/rails g
如果你这样做，你会 运行 进入错误。要解决此问题，请更改 bin/rails 顶部的一些行，如下所示：
# from
ENGINE_ROOT = File.expand_path('../..', __FILE__)
ENGINE_PATH = File.expand_path('../../lib/myengine/engine', __FILE__)
# to
require 'pathname'
ENGINE_ROOT = Pathname.new(__FILE__).realpath + '../..'
ENGINE_PATH = ENGINE_ROOT + 'lib/myengine/engine'
请参阅 ::Rails::Engine.find 的实施，了解补丁为何有效。