哈希删除除特定键以外的所有键

Question

除了给定的密钥之外,我想从哈希中删除每个密钥.

例如:

{
 "firstName": "John",
 "lastName": "Smith",
 "age": 25,
 "address":
 {
     "streetAddress": "21 2nd Street",
     "city": "New York",
     "state": "NY",
     "postalCode": "10021"
 },
 "phoneNumber":
 [
     {
       "type": "home",
       "number": "212 555-1234"
     },
     {
       "type": "fax",
       "number": "646 555-4567"
     }
 ]
}

我想删除除"firstName"和/或"address"之外的所有内容

谢谢

Answer 1

怎么样slice？

hash.slice('firstName', 'lastName')
 # => { 'firstName' => 'John', 'lastName' => 'Smith' }

Answer 2

其他一些选择:

h.select {|k,v| ["age", "address"].include?(k) }

或者你可以这样做:

class Hash
  def select_keys(*args)
    select {|k,v| args.include?(k) }
  end
end

所以你现在可以说:

h.select_keys("age", "address")

Answer 3

如果您使用Rails，请考虑ActiveSupportexcept()方法：http://apidock.com/rails/Hash/ except

hash = { a: true, b: false, c: nil}
hash.except!(:c) # => { a: true, b: false}
hash # => { a: true, b: false }

Answer 4

哈希#select做你想要的:

   h = { "a" => 100, "b" => 200, "c" => 300 }
   h.select {|k,v| k > "a"}  #=> {"b" => 200, "c" => 300}
   h.select {|k,v| v < 200}  #=> {"a" => 100}

编辑(评论):

假设h是上面的哈希:

h.select {|k,v| k == "age" || k == "address" }

Answer 5

hash = { a: true, b: false, c: nil }
hash.extract!(:c) # => { c: nil }
hash # => { a: true, b: false }