require 'csv'; CSV.generate { |csv| csv << {a: 1, b: 2} } throws undefined method 'collect' for nil

[dorianmariecom]

What's weird is that it works with structs (and arrays of course) but not with hashes

>> require 'csv'; CSV.generate { |csv| csv << {a: 1, b: 2} }
/Users/dorianmariefr/.asdf/installs/ruby/3.3.4/lib/ruby/gems/3.3.0/gems/csv-3.3.0/lib/csv/writer.rb:36:in `<<': undefined method `collect' for nil (NoMethodError)

        row = @headers.collect {|header| row[header]}
                      ^^^^^^^^
	from /Users/dorianmariefr/.asdf/installs/ruby/3.3.4/lib/ruby/gems/3.3.0/gems/csv-3.3.0/lib/csv.rb:2373:in `<<'
	from (irb):2:in `block in <top (required)>'
	from /Users/dorianmariefr/.asdf/installs/ruby/3.3.4/lib/ruby/gems/3.3.0/gems/csv-3.3.0/lib/csv.rb:1410:in `generate'
	from (irb):2:in `<main>'
	from <internal:kernel>:187:in `loop'
	from /Users/dorianmariefr/.asdf/installs/ruby/3.3.4/lib/ruby/gems/3.3.0/gems/irb-1.14.0/exe/irb:9:in `<top (required)>'
	from /Users/dorianmariefr/.asdf/installs/ruby/3.3.4/bin/irb:25:in `load'
	from /Users/dorianmariefr/.asdf/installs/ruby/3.3.4/bin/irb:25:in `<main>'

[kou]

You need to specify headers:: CSV.generate(headers: [:a, :b]) {|csv| csv << {a: 1, b: 2}}