Cldr.Number custom formatter

Questions / Help
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1

Hi

I have been going through the Cldr docs and I don’t see a clear way to do this.

How can I configure Cldr so I can overwrite the to_string function for certain things?

In particular I want to write the formatter so money:

<%= @money %>

is displayed as "$20" if the amount is {:USD, 20} and displayed as "$20.10" if the amount is {:USD, "20.10"}.
I know I can use Money.to_string with formatting options but I want to keep it simple for other devs and have custom Cldr formatter.

Anyone have any idea or pointers to help me out?

2

If this in phoenix templates? If so then you likely want to implement Phoenix.HTML.Safe for the Money struct.

2 Likes
3

I’m using Money v5.7.4 — Documentation
It already has the Html.Safe protocol implemented.

4

OK cool it finally “clicked” for me. I just put this in my code:

  defimpl Phoenix.HTML.Safe, for: Money do
    def to_iodata(money) do
      "this is how I do it!"
      |> Phoenix.HTML.Safe.to_iodata()
    end
  end

and now my money looks however I want it to look. Thanks @LostKobrakai

5

Oh, interesting. I’ll look at adding that as an implementation on the next version of ex_money. I’m only just now getting back to web dev and hadn’t realised there is both the Html.Safe and Phoenix.HTML.Safe protocols (and maybe there isn’t a difference any more!)

D’Oh, should have read my own code first. This is the implementation:

  defimpl Phoenix.HTML.Safe, for: Money do
    def to_iodata(money) do
      Phoenix.HTML.Safe.to_iodata(Money.to_string!(money))
    end
  end

Does it not do what you expect?

You can actually store formatting options in a Money.t if you need - that capability was primarily added to support this protocol. Of course if thats not enough you can certainly do your own implementation as you showed.

Example

iex> m = Money.new(:USD, 1234, format: :long)
#Money<:USD, 1234>
iex> Money.to_string m                       
{:ok, "1,234 US dollars"}
1 Like
6

For illumination, here is exactly the code I ended up writing:

  defimpl Phoenix.HTML.Safe, for: Money do
    def to_iodata(%Money{amount: %Decimal{coef: coef, exp: 0}} = money) when is_integer(coef) do
      money
      |> Money.to_string!(fractional_digits: 0)
      |> HTML.Safe.to_iodata()
    end

    def to_iodata(money) do
      money
      |> Money.to_string!()
      |> HTML.Safe.to_iodata()
    end
  end

So you can see there are 2 functions.

The 2nd function is the “fallback” function and is identical to the existing Money source code.

The 1st function pattern-matches for “integer” money amounts.

The result of this is displaying money as “$20.34” when it is not an integer amount and as “$20” when it is an integer amount (there is no ".00" at the end).

UPDATE: this code actually breaks my deployments. I get an error from mix release:

** (Mix) Duplicated modules:
     'Elixir.Phoenix.HTML.Safe.Money' specified in my_module and ex_money

I even get this error with elixirc_options: [ignore_module_conflict: true]] in my project in mix.exs.

7

I don’t understand this. Can you provide an example?

UPDATE: ignore this. I understand you mean Money.new(..., options). Sadly, this doesn’t fit my needs.

I need to fully override the protocol. Would it be possible to make this overrideable?

8

Thanks for the explanation and I understand the use case. Let me think on this and revert soon.

1 Like
9

As of commit 8c14f4f there is a compile-time option to configure whether or not the default protocol implementation is defined. The changelog entry is:

  • Add :define_phoenix_html_safe as a compile-time configuration option. The default is true. If set to a falsy value then the default protocol implementation will not be generated and users can define their own implementation.

Basically, in config.exs and friends:

config :ex_money,
  define_phoenix_html_safe: false

The commit is on a development branch that will be published Lunar New Year’s Day (next Tuesday) and therefore can’t really be used easily as a GitHub dependency.

If the need becomes urgent I can do a backport to the current main branch and publish a release, but I’d prefer to wait until Tuesday if thats possible. Let me know?

1 Like
10

It’s really cool that you decided to make this possible.

I wonder if maybe there is a more extensible approach?

What comes to mind is a compile-time configuration option :exclude_protocol_implementations with default []. If set to, e.g. [Gringotts.Money, Inspect, Jason.Encoder] then these 3 protocol implementations would not be defined.

For my case, I would then only need exclude_protocol_implementations: [Phoenix.HTML.Safe].

I think this approach will be easier for future customizations. Also the name exclude_protocol_implementations provides immediate insight into what is happening, even which file in the source code to check.

I left some comments on the commit, to illustrate what I’m thinking.

Thanks again!

P.S. This is not urgent at all. We are using a show_money view helper until something more elegant is possible. :+1:

11

I have pushed commit 72f78b4 to ex_money master branch implementing your suggestion. The changelog entry reads:

Enhancements

  • Adds configuration option :exclude_protocol_implementations to omit generating implementations for one or more protocols from the list Json.Encoder, Phoneix.HTML.Safe and Gringotts.Money. Thanks to @jgough-playoxygen for the suggestion.

If you have a chance to take it for a spin from GitHub that would be great. Pending your feedback I’ll then publish to hex.

5 Likes
12

I used the latest commit with our project and it works perfectly. Thanks @kip for your consistently beautiful and prolific work.

1 Like
13

For posterity, my function now looks like this:

  defimpl Phoenix.HTML.Safe, for: Money do
    def to_iodata(%Money{amount: %Decimal{coef: coef, exp: 0}} = money) when is_integer(coef) do
      money
      |> Money.to_string!(fractional_digits: 0)
      |> HTML.Safe.to_iodata()
    end

    @simple_currencies [:USD, :EUR]
    def to_iodata(%Money{amount: %Decimal{coef: coef, exp: -2}, currency: currency} = money)
        when rem(coef, 100) == 0 and currency in @simple_currencies do
        money
        |> Money.to_string!(fractional_digits: 0)
        |> HTML.Safe.to_iodata()
      end

    def to_iodata(money) do
      money
      |> Money.to_string!()
      |> HTML.Safe.to_iodata()
    end
  end
1 Like
14

Thanks for the feedback. I’ve published ex_money version 5.8.0 with this new configuration option :exclude_protocol_implementations.

1 Like