diff options
| -rw-r--r-- | railties/guides/source/active_support_overview.textile | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/railties/guides/source/active_support_overview.textile b/railties/guides/source/active_support_overview.textile index 352feb96fb..ac326d5a24 100644 --- a/railties/guides/source/active_support_overview.textile +++ b/railties/guides/source/active_support_overview.textile @@ -788,7 +788,19 @@ h3. Extensions to +BigDecimal+ h3. Extensions to +Enumerable+ -... +h4. +group_by+ + +Ruby 1.8.7 and up define +group_by+, and Active Support does it for previous versions. + +This iterator takes a block and builds an ordered hash with its return values as keys. Each key is mapped to the array of elements for which the block returned that value: + +<ruby> +entries_by_surname_initial = address_book.group_by do |entry| + entry.surname[0, 1].upcase +end +</ruby> + +WARNING. Active Support redefines +group_by+ in Ruby 1.8.7 so that it still returns an ordered hash. h3. Extensions to +Array+ |