From: dawid.janczak@...
Date: 2014-07-28T14:32:18+00:00
Subject: [ruby-core:64099] [ruby-trunk - Bug #10013] [CSV] Yielding all	elements from a row

Issue #10013 has been updated by Dawid Janczak.


First of all sorry for the late answer Andrew.

Checking arity was one thing I was considering. You're right that the arity of the block might not match the number of items, but that works fine with arrays.
<code>
foo = [[1, 2], [3, 4]]
foo.each { |el| p el } # => prints [1, 2] then [3, 4]
foo.each { |el1, el2| p el2 } # => prints 2 then 4
foo.each { |el1, el2, el3| p el3 } # => prints nil then nil
</code>
This is basically the same behaviour as parallel assignment with more LVals than RVals.

Another thing I was considering was to always yield CSV::Row objects.

----------------------------------------
Bug #10013: [CSV] Yielding all elements from a row
https://bugs.ruby-lang.org/issues/10013#change-48111

* Author: Dawid Janczak
* Status: Assigned
* Priority: Normal
* Assignee: James Gray
* Category: lib
* Target version: current: 2.2.0
* ruby -v: ruby 2.2.0dev (2014-07-06 trunk 46722) [x86_64-linux]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN
----------------------------------------
Let's say I have the following CSV file:
col1,col2,col3
1,2,3
4,5,6
(...)

I want to iterate over values yielding them to a block. I can do that like this:
`CSV.foreach('file.csv') { |col1, col2, col3| print col2 + " " } # => "col2 2 5"`
This works fine, but I would like to skip the headers:
`CSV.foreach('file.csv', headers: true) { |col1, col2, col3| print col2 + " " } # => NoMethodError`

CSV yields rows as arrays if headers option is not specified and destructuring works fine.
When headers option is specified however, CSV::Row objects are yielded instead and destructuring fails.

It would be nice to have both scenarios working in the same manner, but I don't know how to approach this. Calling to_a on yielded row (https://github.com/ruby/ruby/blob/trunk/lib/csv.rb#L1731) worked, but obviously this would break when people actually expect CSV::Row instance. Any ideas?



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