how to permit an array with strong parameters

Question

I have a functioning Rails 3 app that uses has many  through associations which is not  as I remake it as a Rails 4 app  letting me save ids from the associated model in the Rails 4 version    These are the three relevant models are the same for the two versions    Categorization rb  class Categorization  lt  ActiveRecord  Base    belongs to  question   belongs to  category end   Question rb  has many  categorizations has many  categories  through   categorizations   Category rb  has many  categorizations has many  questions  through   categorizations   In both apps  the category ids are getting passed into the create action like this     question   gt   question content   gt  How do you spell car     question details   gt  blah     category ids   gt       2      In the Rails 3 app  when I create a new question  it inserts into questions table and then into the categorizations table    SQL  82 1ms   INSERT INTO  questions    accepted answer id    city    created at    details    province    province id    question    updated at    user id   VALUES                                 accepted answer id   nil     city    dd      created at   Tue  14 May 2013 17 10 25 UTC  00 00     details    greyound       province   nil     province id   2     question    Whos  the biggest dog in the world      updated at   Tue  14 May 2013 17 10 25 UTC  00 00     user id   53     SQL  0 4ms   INSERT INTO  categorizations    category id    created at    question id    updated at   VALUES                  category id   2     created at   Tue  14 May 2013 17 10 25 UTC  00 00     question id   66     updated at   Tue  14 May 2013 17 10 25 UTC  00 00     In the rails 4 app  after it processes the parameters in QuestionController create  I m getting this error in the server logs  Unpermitted parameters  category ids   and the question is only getting inserted into the questions table    0 2ms   BEGIN   SQL  67 6ms   INSERT INTO  questions    city    created at    province id    question content    question details    updated at    user id   VALUES   1   2   3   4   5   6   7  RETURNING  id      city    dd      created at   Tue  14 May 2013 17 17 53 UTC  00 00     province id   3     question content    How s your car       question details    is it runnign      updated at   Tue  14 May 2013 17 17 53 UTC  00 00     user id   12       31 9ms   COMMIT   Although I am not storing the category ids on the Questions model  I set category ids as a permitted parameter in the questions controller     def question params        params require  question  permit  question details   question content   user id   accepted answer id   province id   city   category ids      end   Can anyone explain how I m supposed to save the category ids   Note  there is no create action in the categories controller rb of either app   These are the three tables that are the same in both apps   create table  questions   force  true do  t      t text      question details      t string    question content      t integer   user id      t integer   accepted answer id      t datetime  created at      t datetime  updated at      t integer   province id      t string    city    end   create table  categories   force  true do  t      t string    name      t datetime  created at      t datetime  updated at    end    create table  categorizations   force  true do  t      t integer   category id      t integer   question id      t datetime  created at      t datetime  updated at    end   Update  This is the create action from the Rails 3 app    def create        question   Question new params  question         respond to do  format        if  question save         format html   redirect to  question  notice   Question was successfully created             format json   render json   question  status   created  location   question         else         format html   render action   new            format json   render json   question errors  status   unprocessable entity         end     end end   This is the create action from the Rails 4 app     def create        question   Question new question params          respond to do  format        if  question save         format html   redirect to  question  notice   Question was successfully created             format json   render json   question  status   created  location   question         else         format html   render action   new            format json   render json   question errors  status   unprocessable entity         end     end     end   This is the question params method   private     def question params        params require  question  permit  question details   question content   user id   accepted answer id   province id   city   category ids      end

User · Answer

It should be like  params permit  id   gt        Also since rails version 4  you can use   params permit id

User · Answer

when you want to permit multiple array fields you will have to list array fields at last while permitting  as given - params require  questions  permit  question   user id  answers      selected answer         this works

User · Answer

If you want to permit an array of hashes or an array of objects from the  perspective of JSON   params permit  foo  array    key1   key2     2 points to notice here    array should be the last argument of the permit method  you should specify keys of the hash in the array  otherwise you will get an error Unpermitted parameter  array  which is very difficult to debug in this case

User · Answer

If you have a hash structure like this   Parameters    link   gt   title   gt  Something    time span   gt    start   gt  2017-05-06T16 00 00 000Z    end   gt  2017-05-06T17 00 00 000Z        Then this is how I got it to work   params require  link  permit  title  time span     start   end

User · Answer

I can t comment yet but following on Fellow Stranger solution you can also keep nesting in case you have keys which values are an array  Like this   filters     name   test name   values    test value 1    test value 2        This works   params require  model  permit filters     name  values

User · Answer

This https   github com rails strong parameters seems like the relevant section of the docs      The permitted scalar types are String  Symbol  NilClass  Numeric  TrueClass  FalseClass  Date  Time  DateTime  StringIO  IO    ActionDispatch  Http  UploadedFile and Rack  Test  UploadedFile       To declare that the value in params must be an array of permitted scalar values map the key to an empty array   params permit  id   gt         In my app  the category ids are passed to the create action in an array   category ids   gt       2      Therefore  when declaring strong parameters  I explicitly set category ids to be an array  params require  question  permit  question details   question content   user id   accepted answer id   province id   city   category ids   gt        Works perfectly now    IMPORTANT  As  Lenart notes in the comments  the array declarations must be at the end of the attributes list  otherwise you ll get a syntax error

[ruby-on-rails] how to permit an array with strong parameters

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