Rails 4 checkboxes of strings never return an empty array

Question

I have an array of strings that is the result of a multiple-choice checkbox, when there is no choice in the checkbox the array doesn't change and the result is the last array saved! I'd like to show something like " " when the checkbox has no value selected. ``` <%= f.label :disposizione_campionamento,"Disposizione" %> Random <%= f.check_box :disposizione_campionamento, { :multiple => true }, "Random", nil %> Sistematica <%= f.check_box :disposizione_campionamento,{ :multiple => true }, "Sistematica", nil %> Stratificata <%= f.check_box :disposizione_campionamento,{ :multiple => true }, "Stratificata",nil %>
``` and in the model ``` serialize :disposizione_campionamento, Array ``` If i check Random,Sistematica and Stratificata the result is "Random,Sistematica,Stratificata" as I want but if I modify the array unchecking all the three values the result is ever "Random,Sistematica,Stratificata" when I submit the form I have this in the controller: ``` def create modulo2 = Modulo2.f…

Accepted Answer

When you don't check any checkboxes and submit the form, the content of params is lacking a value saying "none was checked". It just avoid submitting `nil` values for the inputs.

A simple way to solve this, is to set the value of the relevant `params` if not set before:

Rails 4:

```
# your_model controller
def your_model_params # redefining the Strong Params
  params[:your_model][:disposizione_campionamento] ||= []
  params.permit(:whatever).require(:another)
end
```

Rails 3:

```
# your_model controller
before_filter :set_disposizione_campionamento, only: [:update, :create]

def set_disposizione_campionamento
  params[:your_model][:disposizione_campionamento] ||= []
end
```

Rails 4 checkboxes of strings never return an empty array

Solution

Problem