Question

我有一个哈希，其中的键是0、3和5，值是散列。

{0=>{:occurrences=>1, :className=>"class"},
 3=>{:occurrences=>3, :className=>"hello"},
 5=>{:occurrences=>3, :className=>"nah"}}

我该如何实现这样的东西：

h.map { |key| 
  if key[:occurrences] > 2
    key[:occurrences] += 1 
  end
}

我知道此语法无效。我想在满足条件时增加出现值，并且不确定如何访问键的键，但是我希望结果是：

{0=>{:occurrences=>1, :className=>"class"}, 
 3=>{:occurrences=>4, :className=>"hello"}, 
 5=>{:occurrences=>4, :className=>"nah"}}

Answer 1

只是出于好奇：

input.map do |k, v|
  [k, v[:occurrences].to_i > 2 ? v.merge(occurrences: v[:occurrences] + 1) : v]
end.to_h
#⇒ {0=>{:occurrence=>1, :className=>"class"},
#   3=>{:occurrences=>4, :className=>"hello"},
#   5=>{:occurrences=>4, :className=>"nah"}}

Answer 2

要更新现有哈希，您可以简单地调用each_value。它将哈希中的每个值传递给该块，并且您可以在该块内更新该值（基于条件）：

h = {
  0=>{:occurrences=>1, :className=>"class"},
  3=>{:occurrences=>3, :className=>"hello"},
  5=>{:occurrences=>3, :className=>"nah"}
}

h.each_value { |v| v[:occurrences] += 1 if v[:occurrences] > 2 }
#=> {
#     0=>{:occurrences=>1, :className=>"class"},
#     3=>{:occurrences=>4, :className=>"hello"},
#     5=>{:occurrences=>4, :className=>"nah"}
#   }

Answer 3

h = { 0=>{ :occurrences=>1, :className=>"class" },
      3=>{ :occurrences=>3, :className=>"hello" },
      5=>{ :occurrences=>3, :className=>"nah"   } }

f = h.dup

非破坏性案件

h.transform_values do |g|
  g[:occurrences] > 2 ? g.merge(occurrences: g[:occurrences] + 1) : g
end
  #=> { 0=>{ :occurrences=>1, :className=>"class" }, 
  #     3=>{ :occurrences=>4, :className=>"hello" },
  #     5=>{ :occurrences=>4, :className=>"nah"   } }

h == f
  #=> true

破坏性案件

g = h.transform_values! do |g|
  g[:occurrences] > 2 ? g.merge(occurrences: g[:occurrences] + 1) : g
end
  #=> { 0=>{ :occurrences=>1, :className=>"class" },
  #     3=>{ :occurrences=>4, :className=>"hello" },
  #     5=>{ :occurrences=>4, :className=>"nah"   } }
h == g

请参见Hash#transform_values和Hash#transform_values!，它们在MRI v.2.4中首次亮相。请注意，在破坏性情况下，不需要merge!。

Answer 4

例如，我希望返回整个散列，但已更新值：{0 => {：occurrence => 1，：className =>“ class”}， 3 => {：occurrences => 4，：className =>“ hello”}，5 => {：occurrences => 4，：className =>“ nah”}}。如果出现键的值更大比我想增加该值还多两个哈希。

您在这里：

func mapView(_ mapView: MKMapView, didSelect view: MKAnnotationView) {  
         view.clusteringIdentifier = nil  
    }

在值是散列的地方更新散列

4 个答案: