Question

如何将数组哈希与单个哈希进行比较，并返回包含比较结果的新哈希数组。

例如：

stored_hash  = [
    {:a => 1, :b => 2, :c => 3},
    {:a => 1, :b => 3, :c => 4}
]
compare_hash = {:a => 1}
stored_hash.some_function_here(compare_hash)

应该返回：

[
   {:a => 1, :b => 2, :c => 3},
   {:a => 1, :b => 3, :c => 4}
]

虽然这个：

stored_hash  = [
    {:a => 1, :b => 2, :c => 3},
    {:a => 1, :b => 3, :c => 4}
]
compare_hash = {:a => 1, :b => 3}
stored_hash.some_function_here(compare_hash)

应该返回：

[
   {:a => 1, :b => 3, :c => 4}
]

Answer 1

这是一种方法，使用Array#keep_if和Hash#merge

stored_hash.keep_if {|hash| hash.merge(compare_hash) == hash}

Answer 2

你可以这样做：

def matches(stored_hash, compare_hash)
  stored_hash.select do |h|
    h.values_at(*compare_hash.keys) == compare_hash.values
  end
end

stored_hash  = [
    {:a => 1, :b => 2, :c => 3},
    {:a => 1, :b => 3, :c => 4}
]
compare_hash = {:a => 1}

matches(stored_hash, compare_hash)
  #=> [{:a=>1, :b=>2, :c=>3}, {:a=>1, :b=>3, :c=>4}] 

compare_hash = {:a => 1, :b => 3}

matches(stored_hash, compare_hash)
  #=> [{:a=>1, :b=>3, :c=>4}]

Answer 3

除非你想修补Array，否则你不会在stored_hash上调用方法，但你可以这样做：

def some_function(haystack, needle)
  haystack.select do |hash|
    needle.all? { |k,v| hash[k] == v }
  end
end

然后用

调用它

some_function(stored_hash, compare_hash)

另外，请注意您的stored_hash不是哈希，它是一个数组;这个名字有点误导。

Answer 4

另一种方式：

def find_matches(stored_hash, compare_hash)
  stored_hash.find_all {|h| h.to_a & compare_hash.to_a == compare_hash.to_a}
end

compare_hash = {:a=>1, :b=>2}

find_matches(stored_hash, compare_hash)
#=> [{:a=>1, :b=>2, :c=>3}]

compare_hash = {:a=>1}

find_matches(stored_hash, compare_hash)
#=> [{:a=>1, :b=>2, :c=>3}, {:a=>1, :b=>3, :c=>4}]

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4 个答案: