Create a new Ruby CSV object with headers in a single csv.new() line

Question

I'm trying to create a new CSV object with only the header row in it, but the headers are not set until I call read():

[32] pry(main)> c = CSV.new("Keyword,Index,Page,Index in Page,Type,Title,URL", :headers => :first_row, :write_headers => true, :return_headers => true)
=> <#CSV io_type:StringIO encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"" headers:true>
[33] pry(main)> c.headers
=> true
[34] pry(main)> c.read
=> #<CSV::Table mode:col_or_row row_count:1>
[35] pry(main)> c.headers
=> ["Keyword", "Index", "Page", "Index in Page", "Type", "Title", "URL"]

Why is that? Why can't I get a properly working CSV object with my single CSV.new line?

Answer 1

As the documentation will tell you it's treating the string as if it were the contents of a file (i.e. StringIO) so you still have to read the string just as you would any other IO source.

If you want to set the headers explicitly, you pass an array as the :headers parameter.

Answer 2

There does not appear to be a way to do this in one call but you can easily remedy that with a custom method of your own:

Given:

def new_csv(headers, data)
  csv = CSV.new(data, headers: headers, write_headers: true, return_headers: true)
  csv.read
  csv
end

You can call use it as:

csv = new_csv("Header 1, Header 2", "abc,def") 
=> <#CSV io_type:StringIO encoding:UTF-8 lineno:1 col_sep:"," row_sep:"\n" quote_char:"\"" headers:["abc", "def"]>

csv.headers
=> ["Header 1", "Header 2"]

Hope that helps.