Rails：将嵌套属性与strong_params合并
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已经覆盖了其他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？
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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: #, 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: #, 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>}
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的值。
由于sections_attributes是{"0" => first_hash, "1" => second_hash}等forms的“伪数组”，因此您需要一种方法来为每个条目复制一次user 。 您可以使用merge的function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!
如果您发现这对您有用，您可以将其封装在一个方法中，方法是将块内部并使其成为单独的方法，或者将整个内容作为命名方法安装在Parameters类中。
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。