I’m trying to create a macro that converts Type definitions in to a JSON Schema for some client side input validation So far I have this which is working well: crystal play macro introspect(klass) {% klass = klass.resolve %} {% klass_name = klass.name(generic_args: false) %} # see the play…

There’s no way for the parser to know that the argument to introspect is supposed to be evaluated in the type grammar. It’s just parsed as a call to method Bool.| with argument String. As a workaround, you can use Union(String, Int32) to express that it’s a type. Even Union(String | Int32) works. Y…

Following straight-shoota recommendation, you can modify the macro to cater for Union use-case as in crystal play

Thanks for the explanation and workaround! That’s super useful to know

So one final issue that is eluding me, I’m trying to parse JSON::Serializable objects {% properties = {} of Nil => Nil %} {% for ivar in klass.instance_vars %} {% ann = ivar.annotation(::JSON::Field) %} {% unless ann && (ann[:ignore] || ann[:ignore_deserialize]) …

instance_vars can only be used inside methods

Try doing the instrospect call from inside a method that you call

But it works fine when inside a method, so I don’t think it’s correct to do that

I tried this, with the same results module JSON::Serializable macro included macro finished def self.__generate_json_schema__ {% begin %} {% puts "\n\nprocessing JSON::Serializable for #{@type.name}" %} {% puts "Class: #{@type.instance_vars.map(&.…

solved it! module ::Introspect def __generate_json_schema__ {% begin %} {% puts "\n\nprocessing JSON::Serializable for #{@type.name}" %} {% puts "Class: #{@type.instance_vars.map(&.name.stringify)}" %} {% puts "Instance: #{@type.instance.instance_vars.map(&.name…

Unions and macro methods

Help & Support

straight-shoota April 28, 2021, 10:13am 8

Maybe the macro interpreter should error if instance_vars is not called as @type.instance_vars?

TypeNode#instance_vars return empty array?

Topic		Replies	Views
Dynamic union type as a constraint to class method argument type Help & Support	12	415	November 21, 2022
How to make union types macro work also on base classes? Help & Support	1	341	July 24, 2023
Add #nilable? to more macro types Crystal Contrib	9	849	July 17, 2019
Strange compiler error with json serializable type family Help & Support	12	207	August 31, 2024
How to resolve a Path to TypeNode in a macro inside a module Help & Support	5	329	January 16, 2023

Unions and macro methods

Related topics