Question

我想创建一个包含where方法过滤器的自联接。

为此，我将, -> { where location_type: 'Hospital' }添加到模型中：

class Location < ActiveRecord::Base

  has_many :hospitals, class_name: "Location", foreign_key: "parent_id", -> { where location_type: 'Hospital' }
  belongs_to :system, class_name: "Location", foreign_key: "parent_id"

end

不幸的是，这会在Rails控制台中生成错误：

2.0.0-p0 :001 > x = Location.find_by_id(1353)
SyntaxError: /Users/craibuc/Dropbox/Projects/Rails4/emr/app/models/location.rb:3: syntax error, unexpected '\n', expecting =>
    from /Users/craibuc/.rvm/gems/ruby-2.0.0-p0/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:423:in `load'
    from /Users/craibuc/.rvm/gems/ruby-2.0.0-p0/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:423:in `block in load_file'
    from /Users/craibuc/.rvm/gems/ruby-2.0.0-p0/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:615:in `new_constants_in'
    from /Users/craibuc/.rvm/gems/ruby-2.0.0-p0/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:422:in `load_file'
    from /Users/craibuc/.rvm/gems/ruby-2.0.0-p0/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:323:in `require_or_load'
    from /Users/craibuc/.rvm/gems/ruby-2.0.0-p0/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:462:in `load_missing_constant'
    from /Users/craibuc/.rvm/gems/ruby-2.0.0-p0/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:183:in `const_missing'
    from (irb):1
    from /Users/craibuc/.rvm/gems/ruby-2.0.0-p0/gems/railties-4.0.0/lib/rails/commands/console.rb:90:in `start'
    from /Users/craibuc/.rvm/gems/ruby-2.0.0-p0/gems/railties-4.0.0/lib/rails/commands/console.rb:9:in `start'
    from /Users/craibuc/.rvm/gems/ruby-2.0.0-p0/gems/railties-4.0.0/lib/rails/commands.rb:64:in `<top (required)>'
    from bin/rails:4:in `require'
    from bin/rails:4:in `<main>'

documentation表示where子句支持has_many，可能不支持自联接。谁能证实这一点？还有另一种方法吗？

Answer 1

请注意，在提供给关联声明的任何其他选项之前，需要指定lambda范围。

请尝试：

has_many :hospitals, -> { where location_type: 'Hospital' }, class_name: "Location", foreign_key: "parent_id"

Rails 4自联接添加，其中has_many方法导致错误

1 个答案: