Using hashes for structs

struct.rb

# using a predefined hash
hash = { field1: "foo", field2: "bar" }
HashStruct = Struct.new(*hash.keys, keyword_init: true)

hash_struct = HashStruct.new(hash)
hash_struct.field1 # => "foo"
hash_struct.field2 # => "bar"
hash_struct.field3 # => ERROR!


# using an array
ary = [:field1, :field2]
AryStruct = Struct.new(*ary, keyword_init: true)

ary_hash = {}
ary_hash[:field1] = "foo"
ary_hash[:field2] = "bar"

ary_struct = AryStruct.new(ary_hash)
ary_struct.field1 # => "foo"
ary_struct.field2 # => "bar"
ary_struct.field3 # => ERROR!