# Basic parameter validation for dry-initializer?
**URL:** https://discourse.dry-rb.org/t/basic-parameter-validation-for-dry-initializer/1424
**Category:** Support
**Created:** [February 4, 2022, 4:20am UTC](https://discourse.dry-rb.org/t/basic-parameter-validation-for-dry-initializer/1424 "2022-02-04T04:20:19Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@cmer](https://discourse.dry-rb.org/u/cmer)
#### Post date: [February 4, 2022, 4:20am UTC](https://discourse.dry-rb.org/t/basic-parameter-validation-for-dry-initializer/1424/1 "2022-02-04T04:20:19Z")
Hey all,
I am starting to use dry-initializer a lot more to cut back on boilerplate code. It’s awesome!
I am running into a situation where I’d like to perform basic validations for parameters/options passed to the initializer, besides simply enforcing a specific value type. I looked at the doc but couldn’t figure out how to do it.
I’d like to validate two things, for example:
- value passed should be one from a list of allowed values.
- value passed should be an array containing only values from a list of allowed values.
The simplest way to do this seems to have a lambda validating the input, but I don’t think it is possible?
What’s the best to achieve something like described above?
Tia
---
### Author:  [@cmer](https://discourse.dry-rb.org/u/cmer)
#### Post date: [February 4, 2022, 5:07am UTC](https://discourse.dry-rb.org/t/basic-parameter-validation-for-dry-initializer/1424/2 "2022-02-04T05:07:38Z")
Here’s an example of what I mean:
```ruby
class MyClass
extend Dry::Initializer
option :foo, validate: proc { |value| %i[a b c].include?(value)) }
option :bar, type: Dry::Types::Strict::Array, validate: proc { |ary| (ary - %i[foo bar baz]).empty? }
end
MyClass.new(foo: :a, bar: [:foo, :bar]) # valid
MyClass.new(foo: nil, bar: [:fail]) # raises ArgumentError
```
---
### Author:  [@alassek](https://discourse.dry-rb.org/u/alassek)
#### Post date: [February 11, 2022, 1:24am UTC](https://discourse.dry-rb.org/t/basic-parameter-validation-for-dry-initializer/1424/3 "2022-02-11T01:24:26Z")
That’s easily expressable in dry-types
```ruby
Types = Dry::Types(default: :strict)
Class MyClass
extend Dry::Initializer
option :foo, Types::Coercible::Symbol.enum(:a, :b, :c)
option :bar, Types::Array.of(Types::Coercible::Symbol.enum(:foo, :bar, :baz))
end
```