如何基於相同的哈希鍵值合併兩個散列數組？

Question

所以我有散列值的兩個數組：

a = [{"b"=>123,"c"=>456}, {"b"=>456,"c"=>555}] 
b = [{"c"=>456,"d"=>789}, {"b"=>222,"c"=>444}] 

如何將它們連接起來，條件是關鍵c的價值在兩個a和b等同？意思是我希望能夠與a['c'] == b['c']

這種狀況並置是我想要得到的結果是：

final_array = [{"b"=>123,"c"=>456,"d"=>789}, {"b"=>456,"c"=>555}, {"b"=>222,"c"=>444}] 

Answer 1

a = [{"b"=>123,"c"=>456}, {"b"=>456,"c"=>555}] 
b = [{"c"=>456,"d"=>789}, {"b"=>222,"c"=>444}] 

p a.zip(b).map{|h1,h2| h1["c"] == h2["c"] ? h1.merge(h2) : [h1 ,h2]}.flatten 
# => [{"b"=>123, "c"=>456, "d"=>789}, {"b"=>456, "c"=>555}, {"b"=>222, "c"=>444}] 

Answer 2

Enumerable#flat_map和Hash#update用於此目的的最佳方法：

a = [{"b"=>123,"c"=>456}, {"b"=>456,"c"=>555}]  
b = [{"c"=>456,"d"=>789}, {"b"=>222,"c"=>444}] 
p a.zip(b).flat_map{|k,v| next k.update(v) if k["c"] == v["c"];[k,v]} 
# >> [{"b"=>123, "c"=>456, "d"=>789}, {"b"=>456, "c"=>555}, {"b"=>222, "c"=>444}] 

Answer 3

a = [{"b"=>123,"c"=>456}, {"b"=>456,"c"=>555}] 
b = [{"c"=>456,"d"=>789}, {"b"=>222,"c"=>444}] 

def merge_hashes_with_equal_values(array_of_hashes, key) 
    array_of_hashes.sort { |a,b| a[key] <=> b[key] }. 
    chunk { |h| h[key] }. 
    each_with_object([]) { |h, result| result << h.last.inject(&:merge) } 
end 

p merge_hashes_with_equal_values(a + b, 'c') 

# => [{"b"=>222, "c"=>444}, {"c"=>456, "d"=>789, "b"=>123}, {"b"=>456, "c"=>555}] 

首先連接數組，然後傳遞它到散列鍵合併的方法。對該數組進行排序，然後將哈希值在另一個數組中相互合併，這使合併更容易編程。在這裏，我選擇了#chunk來處理用相同的鍵合併檢測連續運行的散列，並使用#each_with_object來編譯最終數組。

由於此方法需要一個數組來處理，所以起始數組的長度不需要相等，並且這些數組的排序並不重要。缺點是操作的密鑰必須包含一個可排序的值（例如，不包含nils）。

這裏又是一個解決問題的方法，這其中使用哈希來構建結果：

def merge_hashes_with_equal_values(array_of_hashes, key) 
    result = Hash.new { |h,k| h[k] = {} } 
    remainder = [] 
    array_of_hashes.each_with_object(result) do |h, answer| 
    if h.has_key?(key) 
     answer[h.fetch(key)].merge!(h) 
    else 
     remainder << h 
    end 
    end.values + remainder 
end