attr_accessor 在模型中返回 nil 而在控制器中返回正确的值

Question

I have a model Assignment with attr_accessor :members

When I send my ajax request I can see in the terminal the params that are passed, and the my attr_accessor is well set "members"=>["", "12", "13"]

Here is an overview:

Parameters: {"utf8"=>"✓", 
 "authenticity_token"=>"YfDZ8VHrrriXLgf2RRHdZtzE8X0V5NFrEOBKZmoCw5mbvqbNKBsUVdBeJSY6HCj4YqcTQi2iiYZFhXx3SYFngw==", 
"assignment"=>{"members"=>["", "12", "13"], ....}

However in my model Assignment the value of members accessor returns always nil :

before_validation :check_members

def check_members
    throw self.members # this throws: UncaughtThrowError (uncaught throw nil)
end

Why am getting nil for members instead the array of values ?

Answer 1

It seems that I needed to specify an "empty array" for the strong parameters, What I had before is this :

params.require(:assignment).permit(:title, :members)

I turned it to

params.require(:assignment).permit(:title, :members => [])

Now it's working :)

A related source : how to permit an array with strong parameters