Tymon Tobolski (@iteamon) header
Tymon Tobolski (@iteamon) profile picture

Tymon Tobolski

@iteamon

Productivity Made Easy with Slack ⏳ Queue, 🔔 Todo, 💸 Expenses, 📝 Memo → https://teapaw.org/t.co/7sfj5jEyI9

 🇵🇱 Poland
teamon.me
Joined February 2010
  • Tweets1.1K
  • Following170
  • Followers578
I wanted to see current Claude usage limits in macOS menubar, so I've asked Claude to do it. All you need is SwiftBar and this script gist.github.com/teamon/e862a…
Image from Tymon Tobolski (@iteamon)
2
127
There is this perfect connection between business and climbing: more vertical = faster progress When it gets horizontal it's easy to fall.
Image from Tymon Tobolski (@iteamon)
3
359
What’s left is to replace the standard JSON middleware with the custom one.
Image from Tymon Tobolski (@iteamon)
Image from Tymon Tobolski (@iteamon)
1
1
231
We can’t change the already implemented protocol for Decimal - we need a little trick. We can create a custom JSON middleware that will wrap every Decimal in into a new struct. When Jason sees that struct it will run our encode implementation that returns skips the quotes
defmodule FloatsAsDecimalsJSON do @behaviour Tesla.Middleware # Create a wrapper struct defstruct [:decimal] # and implement Jason.Encoder to output decimal as number defimpl Jason.Encoder do # output string, but without quotes def encode(%{decimal: decimal}, _opts), do: Decimal.to_string(decimal, :normal) end @json_opts [engine: Jason, engine_opts: [floats: :decimals]] def call(env, next, opts) do opts = Keyword.merge(env.opts, opts) # 1. Wrap Decimals into struct with {:ok, env} <- encode(env), # 2. Encode request body with JSON middleware {:ok, env} <- Tesla.Middleware.JSON.encode(env, @json_opts ++ opts), # 3. Perform the request {:ok, env} <- Tesla.run(env, next), # 4. Decode response body with JSON middleware {:ok, env} <- Tesla.Middleware.JSON.decode(env, @json_opts ++ opts) do {:ok, env} end end defp encode(%Tesla.Env{body: body} = env), do: {:ok, %{env | body: encode(bo

ALT defmodule FloatsAsDecimalsJSON do @behaviour Tesla.Middleware # Create a wrapper struct defstruct [:decimal] # and implement Jason.Encoder to output decimal as number defimpl Jason.Encoder do # output string, but without quotes def encode(%{decimal: decimal}, _opts), do: Decimal.to_string(decimal, :normal) end @json_opts [engine: Jason, engine_opts: [floats: :decimals]] def call(env, next, opts) do opts = Keyword.merge(env.opts, opts) # 1. Wrap Decimals into struct with {:ok, env} <- encode(env), # 2. Encode request body with JSON middleware {:ok, env} <- Tesla.Middleware.JSON.encode(env, @json_opts ++ opts), # 3. Perform the request {:ok, env} <- Tesla.run(env, next), # 4. Decode response body with JSON middleware {:ok, env} <- Tesla.Middleware.JSON.decode(env, @json_opts ++ opts) do {:ok, env} end end defp encode(%Tesla.Env{body: body} = env), do: {:ok, %{env | body: encode(bo

1
115
Jason library already defines encoder for Decimal struct, but it’s not exactly what we need. The decimal will be encoded as string “1.01” instead of just 1.01. This is a very good default, but unfortunately we need to encode it as float.
defmodule GoodClient3 do use Tesla plug Tesla.Middleware.BaseUrl, "http://example.com" plug Tesla.Middleware.JSON, engine: Jason, engine_opts: [floats: :decimals] def bid(price) do post("/bid", %{price: price}) end end

ALT defmodule GoodClient3 do use Tesla plug Tesla.Middleware.BaseUrl, "http://example.com" plug Tesla.Middleware.JSON, engine: Jason, engine_opts: [floats: :decimals] def bid(price) do post("/bid", %{price: price}) end end

{:ok, _env} = GoodClient3.bid(Decimal.new(price)) # sent request body: {"price":"1.01"}

ALT {:ok, _env} = GoodClient3.bid(Decimal.new(price)) # sent request body: {"price":"1.01"}

2
1
212
Now we get price as a Decimal and we can perform safe math on it. What about sending a decimal encoded as float?
{:ok, %{body: %{"price" => price}}} = GoodClient2.price() price # => #Decimal<1.01> Decimal.mult(price, 3) # => #Decimal<3.03>

ALT {:ok, %{body: %{"price" => price}}} = GoodClient2.price() price # => #Decimal<1.01> Decimal.mult(price, 3) # => #Decimal<3.03>

1
1
141
Fortunately, solving this is pretty straightforward. All we need to do is to instruct Tesla’s JSON middleware underlying library Jason to use correct options. (NOTE: You need to have `decimal` package added as a dependency to your project.)
defmodule GoodClient2 do use Tesla plug Tesla.Middleware.BaseUrl, "http://example.com" # Configure Jason to parse floats as decimals plug Tesla.Middleware.JSON, engine: Jason, engine_opts: [floats: :decimals] def price() do get("/price") end end

ALT defmodule GoodClient2 do use Tesla plug Tesla.Middleware.BaseUrl, "http://example.com" # Configure Jason to parse floats as decimals plug Tesla.Middleware.JSON, engine: Jason, engine_opts: [floats: :decimals] def price() do get("/price") end end

1
4
156
Let’s the the price of 1.01 as an example. When using the default JSON middleware it will be parsed as float. It might look good at first sight, but just multiplying it by 3 uncovers the problem.
defmodule GoodClient1 do use Tesla plug Tesla.Middleware.BaseUrl, "http://example.com" plug Tesla.Middleware.JSON def price() do get("/price") end end

ALT defmodule GoodClient1 do use Tesla plug Tesla.Middleware.BaseUrl, "http://example.com" plug Tesla.Middleware.JSON def price() do get("/price") end end

defmodule GoodClient1 do use Tesla plug Tesla.Middleware.BaseUrl, "http://example.com" plug Tesla.Middleware.JSON def price() do get("/price") end end

ALT defmodule GoodClient1 do use Tesla plug Tesla.Middleware.BaseUrl, "http://example.com" plug Tesla.Middleware.JSON def price() do get("/price") end end

1
1
219
When dealing with money one should always stick to precise arithmetic and use integers or decimals, never floats. But what if some API decides to return and accept JSON with values technically encoded as floats? #MyElixirStatus
{ // 😱😱😱 "price": 1.01 }

ALT { // 😱😱😱 "price": 1.01 }

1
2
1
15
1,505
The implementation fits in a tweet. Fully working example: github.com/teamon/tweets/blo…
Image from Tymon Tobolski (@iteamon)
1
5
263
The interface is pretty straightforward. If the "mode" argument is :real all database operations inside the function will be processed as usual. But if it's :dryrun all changes will be rolled back and database will be left untouched.
Image from Tymon Tobolski (@iteamon)
Image from Tymon Tobolski (@iteamon)
1
1
147
Load more