在Rails 4中，可以将额外参数与用户生成的参数合并，如下所示：
params.require(:post).permit([:title, :body]).merge(user: current_user)
也可以包含嵌套属性，如下所示：
params.require(:post).permit([:title, :body, sections_attributes: [:title, :section_type]])
现在，如果我想将额外参数合并到嵌套模型中，该怎么办？我试过这个：
params.require(:post).permit([:title, :body, sections_attributes: [:title, :section_type]]).merge(user: current_user, sections_attributes: [user: current_user])
但是当我之后使用调试器检查params时，我发现user覆盖了另一个section_attributes而不是与它们合并。有没有更好的方法来解决这个问题？
Full backtrace
--------------
- activemodel (4.0.0.rc1) lib/active_model/attribute_methods.rb:436:in `method_missing'
- activerecord (4.0.0.rc1) lib/active_record/attribute_methods.rb:131:in `method_missing'
- activerecord (4.0.0.rc1) lib/active_record/nested_attributes.rb:432:in `block in assign_nested_attributes_for_collection_association'
- activerecord (4.0.0.rc1) lib/active_record/nested_attributes.rb:431:in `assign_nested_attributes_for_collection_association'
- activerecord (4.0.0.rc1) lib/active_record/nested_attributes.rb:322:in `comments_attributes='
- activerecord (4.0.0.rc1) lib/active_record/attribute_assignment.rb:42:in `_assign_attribute'
- activerecord (4.0.0.rc1) lib/active_record/attribute_assignment.rb:53:in `block in assign_nested_parameter_attributes'
- activerecord (4.0.0.rc1) lib/active_record/attribute_assignment.rb:53:in `assign_nested_parameter_attributes'
- activerecord (4.0.0.rc1) lib/active_record/attribute_assignment.rb:33:in `assign_attributes'
- activerecord (4.0.0.rc1) lib/active_record/core.rb:192:in `initialize'
- activerecord (4.0.0.rc1) lib/active_record/inheritance.rb:27:in `new'
- activerecord (4.0.0.rc1) lib/active_record/reflection.rb:189:in `build_association'
- activerecord (4.0.0.rc1) lib/active_record/associations/association.rb:235:in `build_record'
- activerecord (4.0.0.rc1) lib/active_record/associations/has_many_through_association.rb:102:in `build_record'
- activerecord (4.0.0.rc1) lib/active_record/associations/collection_association.rb:114:in `build'
- activerecord (4.0.0.rc1) lib/active_record/associations/collection_proxy.rb:229:in `build'
- app/controllers/forum/topics_controller.rb:16:in `create'
- actionpack (4.0.0.rc1) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
- actionpack (4.0.0.rc1) lib/abstract_controller/base.rb:189:in `process_action'
- actionpack (4.0.0.rc1) lib/action_controller/metal/rendering.rb:10:in `process_action'
- actionpack (4.0.0.rc1) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
- activesupport (4.0.0.rc1) lib/active_support/callbacks.rb:422:in `_run__642753351245287313__process_action__callbacks'
- activesupport (4.0.0.rc1) lib/active_support/callbacks.rb:80:in `run_callbacks'
- actionpack (4.0.0.rc1) lib/abstract_controller/callbacks.rb:17:in `process_action'
- actionpack (4.0.0.rc1) lib/action_controller/metal/rescue.rb:29:in `process_action'
- actionpack (4.0.0.rc1) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
- activesupport (4.0.0.rc1) lib/active_support/notifications.rb:159:in `block in instrument'
- activesupport (4.0.0.rc1) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
- activesupport (4.0.0.rc1) lib/active_support/notifications.rb:159:in `instrument'
- actionpack (4.0.0.rc1) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
- actionpack (4.0.0.rc1) lib/action_controller/metal/params_wrapper.rb:245:in `process_action'
- activerecord (4.0.0.rc1) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
- actionpack (4.0.0.rc1) lib/abstract_controller/base.rb:136:in `process'
- actionpack (4.0.0.rc1) lib/abstract_controller/rendering.rb:44:in `process'
- actionpack (4.0.0.rc1) lib/action_controller/metal.rb:195:in `dispatch'
- actionpack (4.0.0.rc1) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
- actionpack (4.0.0.rc1) lib/action_controller/metal.rb:231:in `block in action'
- actionpack (4.0.0.rc1) lib/action_dispatch/routing/route_set.rb:80:in `dispatch'
- actionpack (4.0.0.rc1) lib/action_dispatch/routing/route_set.rb:48:in `call'
- actionpack (4.0.0.rc1) lib/action_dispatch/journey/router.rb:71:in `block in call'
- actionpack (4.0.0.rc1) lib/action_dispatch/journey/router.rb:59:in `call'
- actionpack (4.0.0.rc1) lib/action_dispatch/routing/route_set.rb:654:in `call'
- request_store (1.0.5) lib/request_store/middleware.rb:9:in `call'
- warden (1.2.1) lib/warden/manager.rb:35:in `block in call'
- warden (1.2.1) lib/warden/manager.rb:34:in `call'
- rack (1.5.2) lib/rack/etag.rb:23:in `call'
- rack (1.5.2) lib/rack/conditionalget.rb:35:in `call'
- rack (1.5.2) lib/rack/head.rb:11:in `call'
- () home/timothythehuman/.rvm/gems/ruby-2.0.0-p0@whistlr/bundler/gems/remotipart-2d6e0949acc2/lib/remotipart/middleware.rb:30:in `call'
- actionpack (4.0.0.rc1) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
- actionpack (4.0.0.rc1) lib/action_dispatch/middleware/flash.rb:241:in `call'
- rack (1.5.2) lib/rack/session/abstract/id.rb:225:in `context'
- rack (1.5.2) lib/rack/session/abstract/id.rb:220:in `call'
- actionpack (4.0.0.rc1) lib/action_dispatch/middleware/cookies.rb:486:in `call'
- activerecord (4.0.0.rc1) lib/active_record/query_cache.rb:36:in `call'
- activerecord (4.0.0.rc1) lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call'
- activerecord (4.0.0.rc1) lib/active_record/migration.rb:366:in `call'
- actionpack (4.0.0.rc1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
- activesupport (4.0.0.rc1) lib/active_support/callbacks.rb:392:in `_run__4051735323972233883__call__callbacks'
- activesupport (4.0.0.rc1) lib/active_support/callbacks.rb:80:in `run_callbacks'
- actionpack (4.0.0.rc1) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
- actionpack (4.0.0.rc1) lib/action_dispatch/middleware/reloader.rb:64:in `call'
- actionpack (4.0.0.rc1) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
- better_errors (0.9.0) lib/better_errors/middleware.rb:84:in `protected_app_call'
- better_errors (0.9.0) lib/better_errors/middleware.rb:79:in `better_errors_call'
- better_errors (0.9.0) lib/better_errors/middleware.rb:56:in `call'
- actionpack (4.0.0.rc1) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
- actionpack (4.0.0.rc1) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
- railties (4.0.0.rc1) lib/rails/rack/logger.rb:38:in `call_app'
- railties (4.0.0.rc1) lib/rails/rack/logger.rb:21:in `block in call'
- activesupport (4.0.0.rc1) lib/active_support/tagged_logging.rb:67:in `block in tagged'
- activesupport (4.0.0.rc1) lib/active_support/tagged_logging.rb:25:in `tagged'
- activesupport (4.0.0.rc1) lib/active_support/tagged_logging.rb:67:in `tagged'
- railties (4.0.0.rc1) lib/rails/rack/logger.rb:21:in `call'
- actionpack (4.0.0.rc1) lib/action_dispatch/middleware/request_id.rb:21:in `call'
- rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
- rack (1.5.2) lib/rack/runtime.rb:17:in `call'
- activesupport (4.0.0.rc1) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
- rack (1.5.2) lib/rack/lock.rb:17:in `call'
- actionpack (4.0.0.rc1) lib/action_dispatch/middleware/static.rb:64:in `call'
- railties (4.0.0.rc1) lib/rails/engine.rb:511:in `call'
- railties (4.0.0.rc1) lib/rails/application.rb:96:in `call'
- rack (1.5.2) lib/rack/content_length.rb:14:in `call'
- thin (1.5.1) lib/thin/connection.rb:81:in `block in pre_process'
- thin (1.5.1) lib/thin/connection.rb:79:in `pre_process'
- thin (1.5.1) lib/thin/connection.rb:54:in `process'
- thin (1.5.1) lib/thin/connection.rb:39:in `receive_data'
- eventmachine (1.0.3) lib/eventmachine.rb:187:in `run'
- thin (1.5.1) lib/thin/backends/base.rb:63:in `start'
- thin (1.5.1) lib/thin/server.rb:159:in `start'
- rack (1.5.2) lib/rack/handler/thin.rb:16:in `run'
- rack (1.5.2) lib/rack/server.rb:264:in `start'
- railties (4.0.0.rc1) lib/rails/commands/server.rb:84:in `start'
- railties (4.0.0.rc1) lib/rails/commands.rb:80:in `block in <top (required)>'
- railties (4.0.0.rc1) lib/rails/commands.rb:75:in `<top (required)>'
- bin/rails:4:in `<main>'
参数：
{"name"=>"stuff", "description"=>"", "topical_id"=>"1", "topical_type"=>"User", "comments_attributes"=>{"0"=>{"body"=>"1111111111111111111"}, "user"=>#<User id: 1, active: true, bio: nil, birthday: nil, image: nil, location: nil, real_name: nil, twitter_name: nil, username: "tbaron", website: nil, whuffie: #<BigDecimal:6365488,'0.0',9(18)>, slug: nil, created_at: "2013-05-31 00:42:28", updated_at: "2013-05-31 00:42:35", email: "alskjdf@alskjdf.com", encrypted_password: "$2a$10$jSrDsC9Ai.yFU5sttCxIiuRBthDUYiy9wWyZnie70qbp...", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 1, current_sign_in_at: "2013-05-31 00:42:35", last_sign_in_at: "2013-05-31 00:42:35", current_sign_in_ip: "127.0.0.1", last_sign_in_ip: "127.0.0.1", confirmation_token: nil, confirmed_at: nil, confirmation_sent_at: nil, unconfirmed_email: nil, failed_attempts: 0, unlock_token: nil, locked_at: nil>}, "user"=>#<User id: 1, active: true, bio: nil, birthday: nil, image: nil, location: nil, real_name: nil, twitter_name: nil, username: "tbaron", website: nil, whuffie: #<BigDecimal:6365488,'0.0',9(18)>, slug: nil, created_at: "2013-05-31 00:42:28", updated_at: "2013-05-31 00:42:35", email: "alskjdf@alskjdf.com", encrypted_password: "$2a$10$jSrDsC9Ai.yFU5sttCxIiuRBthDUYiy9wWyZnie70qbp...", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 1, current_sign_in_at: "2013-05-31 00:42:35", last_sign_in_at: "2013-05-31 00:42:35", current_sign_in_ip: "127.0.0.1", last_sign_in_ip: "127.0.0.1", confirmation_token: nil, confirmed_at: nil, confirmation_sent_at: nil, unconfirmed_email: nil, failed_attempts: 0, unlock_token: nil, locked_at: nil>}
答案 0 :(得分：7)
您调用的merge方法只是通常的Ruby Hash#merge方法。对于merge参数中的每个键，该值将覆盖当前为该键存在的值（如果有）。在这种情况下，您将覆盖sections_attributes。
由于sections_attributes是{"0" => first_hash, "1" => second_hash}形式的“伪数组”，所以您需要一种方法来复制user每个条目一次。您可以通过使用合并的功能来获取更改合并值的块。这是一种方法：
filtered_params = params.require(:post)
.permit([:title,
:body,
sections_attributes: [:title, :section_type]])
additional_params = {user: current_user, sections_attributes: [user: current_user]}
result = filtered_params.merge(additional_params) do |key, oldval, newval|
if newval.is_a? Array
# Arrays are expected to be one-element arrays containing a Hash that is
# supposed to be merged into each element of the currently-existing
# "pseudo-array"
oldval ||= {}
Hash[oldval.map {|k, v| [k, v.merge(newval.first)]}]
elsif newval.is_a? Hash
# Hashes are merged into existing hashes
oldval ||= {}
oldval.merge newval
else
# Other types are passed as-is (and replace any existing value)
newval
end
end
# This marks the newly added parameters as permitted. It's only necessary because we
# made new Hashes when we modified the "pseudo-array"
result.permit!
如果你发现这对你有用，你可以将它封装在一个方法中，或者通过获取块的内部并使它成为一个单独的方法，或者将整个东西作为命名方法安装在{{1 }。class。
另请注意，上面只处理一层递归。比这更深入有点棘手。如果你需要这样做，我很乐意写一个解释。