Rails 4 - Iterate through nested JSON params - ruby-on-rails

Question

I'm passing nested JSON into rails like so:
{
"product": {
"vendor": "Acme",
"categories":
{
"id": "3",
"method": "remove",
},
"categories":
{
"id": "4"
}
}
}
in order to update the category on a product. I am trying to iterate through the categories attribute in my products_controller so that I can add/remove the product to multiple categories at once:
def updateCategory
#product = Product.find(params[:id])
params[:product][:categories].each do |u|
#category = Category.find_by(id: params[:product][:categories][:id])
if params[:product][:categories][:method] == "remove"
#product.remove_from_category(#category)
else
#product.add_to_category(#category)
end
end
end
However, this only uses the second 'categories' ID in the update and doesn't iterate through both.
Example response JSON:
{
"product": {
"id": 20,
"title": "Heavy Duty Aluminum Chair",
"product_price": "47.47",
"vendor": "Acme",
"categories": [
{
"id": 4,
"title": "Category 4"
}
]
}
}
As you can see, it only added the category with ID = 4, and skipped over Category 3.
I'm fairly new to rails so I know I'm probably missing something obvious here. I've played around with the format of the JSON I'm passing in as well but it only made things worse.

Answer 1

You need to change your JSON structure. As you currently have it, the second "categories" reference will override the first one since you can only have 1 instance of a key. To get what you want, you should change it to:
{
"product": {
"vendor": "Acme",
"categories": [
{
"id": "3",
"method": "remove",
},
{
"id": "4"
}
]
}
}
You will also need to change your ruby code to look like:
def updateCategory
#product = Product.find(params[:id])
params[:product][:categories].each do |u|
#category = Category.find_by(id: u[:id])
if u[:method] == "remove"
#product.remove_from_category(#category)
else
#product.add_to_category(#category)
end
end
end