本文介绍了Rails:将嵌套属性与strong_params合并的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
在Rails 4中，可以将额外的参数与用户生成的参数合并，如下所示:
In Rails 4, it's possible to merge extra parameters with user generated ones like so:
params.require(:post).permit([:title, :body]).merge(user: current_user)
还可以像这样包含嵌套属性:
It's also possible to include nested attributes like so:
params.require(:post).permit([:title, :body, sections_attributes: [:title, :section_type]])
现在，如果我想将额外的参数合并到嵌套模型中，该怎么办.我试过了:
Now, what if I wanted to merge extra parameters into a nested model. I tried this:
params.require(:post).permit([:title, :body, sections_attributes: [:title, :section_type]]).merge(user: current_user, sections_attributes: [user: current_user])
但是当我之后用调试器检查参数时，我发现user已经覆盖了另一个section_attributes而不是与它们合并.有没有更好的方法来解决此问题?
But when I check the params with debugger afterwards, I find that user has overwritten the other section_attributes rather than merging with them. Is there a better way to approach this problem?
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: "[email protected]", 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: "[email protected]", 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>}
推荐答案
您正在调用的merge方法只是常规的Ruby Hash#merge方法.对于merge参数中的每个键，该值将覆盖该键当前存在的值(如果有).在这种情况下，您将覆盖sections_attributes的值.
The merge method that you're calling is just the usual Ruby Hash#merge method. For each key in the argument of merge, the value overwrites the value that is currently present for that key, if any. In this case, you are overwriting the value of sections_attributes.
由于sections_attributes是形式为{"0" => first_hash, "1" => second_hash}的伪数组"，依此类推，因此您需要一种方法来为每个条目复制一次user.您可以通过使用合并功能来执行更改合并值的块.这是一种方法:
Since sections_attributes is a "pseudo-array" of the form {"0" => first_hash, "1" => second_hash} and so on, you need a way to duplicate your user once per entry. You can do that by using the ability of merge take a block that changes the merged value. Here's one approach:
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!
如果您发现它适合您，则可以将其封装在方法中，方法是将代码块内部并使其成为一个单独的方法，或者将整个对象作为命名方法安装在Parameters上课.
If you find that this works for you, you could encapsulate this in a method, either by taking the inside of the block and making it a separate method, or by installing the whole thing as a named method on the Parameters class.
还请注意，以上内容仅处理一层递归.比这更深入一点是棘手的.如果您需要这样做，我很乐意写一个说明.
Note also that the above only handles one layer of recursion. Going deeper than this is a bit tricky. If you need to do it, I'd be happy to write up an explanation.
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