ruby - 与 block 一起使用时，ruby Hash#merge 的行为是什么

Question

它似乎没有被记录很多:

hsh.merge(other_hash){|key, oldval, newval| block} → a_hash

http://ruby-doc.org/core/classes/Hash.html#M002880

Answer 1

正如预期的那样，生成的散列将包含一个 block 返回的值，该 block 针对存在于两个正在合并的散列中的每个键:

>> h1 = {:a => 3, :b => 5, :c => 6}
=> {:a=>3, :b=>5, :c=>6}
>> h2 = {:a => 4, :b => 7, :d => 8}
=> {:a=>4, :b=>7, :d=>8}
>> h1.merge h2
=> {:a=>4, :b=>7, :c=>6, :d=>8}
>> h1.merge(h2){|k,v1,v2| v1}
=> {:a=>3, :b=>5, :c=>6, :d=>8}
>> h1.merge(h2){|k,v1,v2| v1+v2}
=> {:a=>7, :b=>12, :c=>6, :d=>8}