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Diffstat (limited to 'railties/guides/source/active_support_overview.textile')
| -rw-r--r-- | railties/guides/source/active_support_overview.textile | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/railties/guides/source/active_support_overview.textile b/railties/guides/source/active_support_overview.textile index 9682a6ee4b..352feb96fb 100644 --- a/railties/guides/source/active_support_overview.textile +++ b/railties/guides/source/active_support_overview.textile @@ -1321,6 +1321,35 @@ def create_has_many_reflection(association_id, options, &extension) end </ruby> +h4. Slicing + +Ruby has builtin support for taking slices out of strings and arrays. Active Support extends slicing to hashes: + +<ruby> +{:a => 1, :b => 2, :c => 3}.slice(:a, :c) +# => {:c => 3, :a => 1} + +{:a => 1, :b => 2, :c => 3}.slice(:b, :X) +# => {:b => 2} # non-existing keys are ignored +</ruby> + +If the receiver responds to +convert_key+ keys are normalized: + +<ruby> +{:a => 1, :b => 2}.with_indifferent_access.slice("a") +# => {:a => 1} +</ruby> + +NOTE. Slicing may come in handy for sanitizing option hashes with a white list of keys. + +There's also +slice!+ which in addition to perform a slice in place returns what's removed: + +<ruby> +hash = {:a => 1, :b => 2} +rest = hash.slice!(:a) # => {:b => 2} +hash # => {:a => 1} +</ruby> + h4. Indifferent Access The method +with_indifferent_access+ returns an +ActiveSupport::HashWithIndifferentAccess+ out of its receiver: |