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我想创建一个包含where方法过滤器的自联接。

为此，我, -> { where location_type: 'Hospital' }在模型中添加了：

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 控制台中产生错误：

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>'

文档表明一个where子句支持 a has_many，也许它不支持自联接。谁能证实这一点？还有另一种方法吗？

4

1 回答 1

1

请注意，需要在提供给关联声明的任何其他选项之前指定 lambda 范围。

请试试：

has_many :hospitals, -> { where location_type: 'Hospital' }, class_name: "Location", foreign_key: "parent_id"
于 2013-08-27T01:07:37.400 回答