find_index
find_index(*args)
public
Returns the index of the first object in ary such that the object is
to obj.
If a block is given instead of an argument, returns the index of the first object for which the block returns true. Returns nil if no match is found.
See also Array#rindex.
An Enumerator is returned if neither a block nor argument is given.
a = [ "a", "b", "c" ] a.index("b") #=> 1 a.index("z") #=> nil a.index { |x| x == "b" } #=> 1
Using block version in Ruby < 1.8.7
The block usage was added in 1.8.7, so to get the same functionality in an earlier version of Ruby, you need to utilize the find method.
Here is a quick example:
match = list.find { |l| l.owner == myself } match_index = list.index(match)
If you do some gymnastics, you can have it on one line without extra variables:
match_index = list.index(list.find { |l| l.owner == myself })
Using find_index to return first match. Profit!
This example shows how to use find_index to return a result as soon as the first occurrence of what you are looking for is found.
Code example
class Widget < Struct.new(:name, :profit); end class WidgetManager def initialize(*widgets) @widgets = widgets end def is_any_widget_profitable? @widgets.find_index { |w| w.profit > 0 } # <== usage! end end wm = WidgetManager.new(Widget.new('a', -100), Widget.new('b', 200), Widget.new('c', 300)) wm.is_any_widget_profitable? # => 1 (wm.is_any_widget_profitable?) ? 'some profit' : 'all loss' # => "some profit" wm = WidgetManager.new(Widget.new('a', -100), Widget.new('b', -200), Widget.new('c', -300)) wm.is_any_widget_profitable? # => nil (wm.is_any_widget_profitable?) ? 'some profit' : 'all loss' # => "all loss"