ruby - When is an enumerator useful? -

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an enumerator object can created calling methods without passing block, example array#reject:

(1..3).reject.to_a # => [1, 2, 3]

is rule of ruby easier chaining or there other way pass behavior enumerator?

is rule of ruby easier chaining

yes, reason exactly. easy chaining of enumerators. consider example:

ary = ['alice', 'bob', 'eve']  records = ary.map.with_index |item, idx|   {     id: idx,     name: item,   } end  records # => [{:id=>0, :name=>"alice"}, {:id=>1, :name=>"bob"}, {:id=>2, :name=>"eve"}]

map yields each element with_index, slaps item index on top of , yields block. block returns value with_index, returns map (does thing, mapping, and) returns caller.


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