[dry-types] Coercing String with decimal to Integer fails

Support dry-types
1

Using Types::Params::Integer to convert a String containing a number with a decimal point results in an error.
Dry::Types::Coercions::Params.to_int("1.5") = invalid value for Integer(): "1.5" (Dry::Types::CoercionError)

I assumed the converter would act identically to Ruby’s String#to_i and remove any digits after the decimal point.
"1.5".to_i = 1

Right now I’m adding a check before performing a call using Types::Params::Integer. If the value is a String, I use .to_i instead. But that feels like terrible hack. Can anyone suggest a better way?

2

It’s purposefully not acting as the built-in coercion as it’s not strict enough. You can define your own coercion like this:

irb(main):005:0> MyInt = Types.Constructor(Integer, &:to_i)
=> #<Dry::Types[Constructor<Nominal<Integer> fn=.to_i>]>
irb(main):006:0> MyInt["1.5"]
=> 1

However, notice that this may lead to all kinds of weird behavior, like this:

irb(main):008:0> MyInt["afa1.5afa"]
=> 0

This is why params coercions are much more strict about the input.

3

Ah, got it, that makes sense. Thank you for letting me know the right way to define my own coercion.

1 Like