Insert multiple where clause based on user input params in Ecto query

The good way is to reduce a criteria list into a query…

It will be helpful if you provide me the code how to achieve for above code as I am learning so there are lots of new things for me

Something like this… (it’s related to a User)

  def list_users_query(criteria \\ []) do
    query = from p in User

    Enum.reduce(criteria, query, fn
      {:limit, limit}, query ->
        from p in query, limit: ^limit

      {:offset, offset}, query ->
        from p in query, offset: ^offset

      {:filter, filters}, query ->
        filter_with(filters, query)

      {:order, order}, query ->
        from p in query, order_by: [{^order, ^@order_field}]

      {:preload, preloads}, query ->
        from p in query, preload: ^preloads

      arg, query ->
        Logger.info("args is not matched in query #{inspect arg}")
        query
    end)
  end

  defp filter_with(filters, query) do
    Enum.reduce(filters, query, fn
      {:name, name}, query ->
        pattern = "%#{name}%"
        from q in query, where: ilike(q.name, ^pattern)
    end)
  end

Then You could do…

iex> Accounts.list_users filter: [name: "dmi"], limit: 1 

How to write the condition if there is no filter I mean if user has landed to product listing page but not applied any filter I think in that case it will not work.

How can I pass order by clause while using reduce criteria ?

It’s optional… If You don’t pass criteria, it will not be used

You can also pass an order parameter.