Ruby: Dynamically creating function call arguments list from an array

Question

I'm creating a spreadsheet using the axlsx gem. I'd like to set fixed width to on all spreadsheet columns and I need to call the function

def column_widths(*widths)
  widths.each_with_index do |value, index|
    next if value == nil
    Axlsx::validate_unsigned_numeric(value) unless value == nil
    find_or_create_column_info(index).width = value
  end
end

defined in the Axlsx::Worksheet with an arbitrary number of column widths. E.g. `sheet.column_width(20, 20, ..., 20). My method call looks like

sheet.column_widths [20]*headers.length

and it result in the error

ActionView::Template::Error (Invalid Data [20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20] for Invalid column width. must be [Fixnum, Integer, Float].

How can I dynamically create a proper method call for the unknown number of columns?

What about sheet.column_widths(*[20]*headers.length) ?

MrYoshiji
– MrYoshiji

2014-10-14 17:01:11 +00:00
Commented Oct 14, 2014 at 17:01 — MrYoshiji
– MrYoshiji, Commented Oct 14, 2014 at 17:01
That works. Thanks! Would you like to post an answer?

sakovias
– sakovias

2014-10-14 17:10:11 +00:00
Commented Oct 14, 2014 at 17:10 — sakovias
– sakovias, Commented Oct 14, 2014 at 17:10

MrYoshiji · Accepted Answer · 2014-10-14 17:45:19Z

1

Your problem is that the method column_widths is defined like this:

def column_widths(*widths)
  # some stuff

The splatter operator * present in the arguments *widths means that you can have from 1 to N (where N > 1) arguments. You are trying to use this method with an array of Integer, instead you should pass each Integer as single argument, something like:

sheet.column_widths(20, 20, 20, 20, #etc...

But this is not the best way to do it. One better way to use these arguments is to also use the splatter operator:

sheet.column_widths(*[20]*headers.length)
                   #^ This is the splatter operator

A very explicit example of the utility of the splatter operator (in my IRB console, Ruby 1.9.3p489):

ann, marc, john = *['Ann', 'Marc', 'John']
# => ["Ann", "Marc", "John"] 
ann
# => "Ann"

Some stuff about the splatter operator: http://4loc.wordpress.com/2009/01/16/the-splat-operator-in-ruby/

answered Oct 14, 2014 at 17:45

MrYoshiji

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1 Comment

mu is too short Over a year ago

You could also widths.flatten.each_with_index to make the interface a little more flexible and DWIMy.

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