Question

我有以下代码：

default = {:id => 0, :detail =>{:name=>"Default", :id => ""}}
employees = {}

nr = (0..3).to_a 
nr.each do |n|
    employee = default
    employee[:id] = n
    employee[:detail][:name] = "Default #{n}"
    employee[:detail][:id] = "KEY-#{n}"
    employees[n] = employee
end
puts employees

我希望:id哈希中的密钥:detail的值为KEY-0，KEY-1，KEY-2。

Answer 1

您需要编组默认值才能复制

default = {id: 0, detail: {name: "Default", id:""}}
employees = {}
4.times do |n|
  employees[n] = Marshal.load(Marshal.dump(default))
  employees[n][:id] = n
  employees[n][:detail][:name] = "Default #{n}"
  employees[n][:detail][:id] = "KEY-#{n}"
end
puts employees

输出

{0=>{:id=>0, :detail=>{:name=>"Default 0", :id=>"KEY-0"}}, 1=>{:id=>1, :detail=>{:name=>"Default 1", :id=>"KEY-1"}}, 2=>{:id=>2, :detail=>{:name=>"Default 2", :id=>"KEY-2"}}, 3=>{:id=>3, :detail=>{:name=>"Default 3", :id=>"KEY-3"}}}

您可以阅读此帖子Cloning an array with its content

<强> ADDED

在这里你有一个减少版本，如果你想要的话应该更快。

employees = {}
4.times { |n| employees[n]={id: n, detail: {name: "Default #{n}", id:"KEY-#{n}"}} }
puts employees

Answer 2

您只需要更改：

default = { :id=>0, :detail=>{ :name=>"Default", :id=>"" } }

到

def default
  {}.merge(:id=>0, :detail=>({}.merge(:name=>"Default", :id=>"")))
end

但是，嘿，虽然我们在这里，但我们也可以将其余部分用于Ruby-ize：

employees = (0..3).map do |n|
    employee = default
    employee[:id] = n
    employee[:detail][:name] = "Default #{n}"
    employee[:detail][:id] = "KEY-#{n}"
    employee
end
  #=> [{:id=>0, :detail=>{:name=>"Default 0", :id=>"KEY-0"}},
  #    {:id=>1, :detail=>{:name=>"Default 1", :id=>"KEY-1"}},
  #    {:id=>2, :detail=>{:name=>"Default 2", :id=>"KEY-2"}},
  #    {:id=>3, :detail=>{:name=>"Default 3", :id=>"KEY-3"}}]

让我们确认我们正在制作default

的深层副本

employees[0][:detail][:id] = "cat"
employees
  #=> [{:id=>0, :detail=>{:name=>"Default 0", :id=>"cat"}},
  #    {:id=>1, :detail=>{:name=>"Default 1", :id=>"KEY-1"}},
  #    {:id=>2, :detail=>{:name=>"Default 2", :id=>"KEY-2"}},
  #    {:id=>3, :detail=>{:name=>"Default 3", :id=>"KEY-3"}}]

您更常见的是这样写的：

employees = (0..3).map do |n|
  default.merge(:id=>n, :detail=>{:name=>"Default #{n}", :id=>"KEY-#{n}"})
end
  #=> [{:id=>0, :detail=>{:name=>"Default 0", :id=>"cat"}},
  #    {:id=>1, :detail=>{:name=>"Default 1", :id=>"KEY-1"}},
  #    {:id=>2, :detail=>{:name=>"Default 2", :id=>"KEY-2"}},
  #    {:id=>3, :detail=>{:name=>"Default 3", :id=>"KEY-3"}}]

正如其他答案所建议的，你可以这样做：

class Object
  def deep_copy
    Marshal.load(Marshal.dump(self))
  end
end

然后你可以写：

default = { :id=>0, :detail=>{ :name=>"Default", :id=>"" } }
employees = (0..3).map do |n|
  default.deep_copy.merge(:id=>n, :detail=>{:name=>"Default #{n}",
    :id=>"KEY-#{n}"})
end
  #=> [{:id=>0, :detail=>{:name=>"Default 0", :id=>"KEY-0"}},
  #    {:id=>1, :detail=>{:name=>"Default 1", :id=>"KEY-1"}},
  #    {:id=>2, :detail=>{:name=>"Default 2", :id=>"KEY-2"}},
  #    {:id=>3, :detail=>{:name=>"Default 3", :id=>"KEY-3"}}]

这样做的好处是，如果您更改default，则无需进行其他更改。

Answer 3

您在每次迭代中都会生成一个浅表副本，即每次使用上一次迭代中计算的值覆盖每个副本。您可以尝试使用以下哈希哈希默认模式进行深层复制：

<html>
<head>
<title>Webpage</title>
<link href="http://getbootstrap.com/dist/css/bootstrap.min.css" rel="stylesheet" >
<link href="http://getbootstrap.com/examples/jumbotron-narrow/jumbotron-narrow.css" rel="sylesheet">
</head>
<body>
<style type=text/css>
    background-image: url("static/images/back.png");
</style>
<p>Does the Image Work? </p>
</body>
</html>

Demonstration

使用默认哈希的结构创建哈希哈希

3 个答案: