Ruby Hash fetch函数

Hash#fetch()是一个Hash类方法，它从散列中返回一个给定键的值。如果没有其他参数，它将引发一个KeyError异常。

语法。Hash.fetch()

参数：哈希值

返回：从给定键的哈希值中获取数值

例子 #1 :

# Ruby code for Hash.fetch() method
  
# declaring Hash value
a = { "a" => 100, "b" => 200 }
  
# declaring Hash value
b = {"a" => 100}
  
# declaring Hash value
c = {"a" => 100, "c" => 300, "b" => 200}
  
# Handling no key argument
# fetch? Value
puts "Hash a fetch form : #{a.fetch("x"){|el| "Not present, #{el}"}}\n\n"

输出:

Hash a fetch form : Not present, x

例子 #2 :

# Ruby code for Hash.fetch() method
  
# declaring Hash value
a = { "a" => 100, "b" => 200 }
  
# declaring Hash value
b = {"a" => 100}
  
# declaring Hash value
c = {"a" => 100, "c" => 300, "b" => 200}
  
# fetch Value
puts "Hash a fetch form : #{a.fetch("a")}\n\n"
  
puts "Hash b fetch form : #{b.fetch("a")}\n\n"
  
puts "Hash c fetch form : #{c.fetch("b")}\n\n"

输出:

Hash a fetch form : 100

Hash b fetch form : 100

Hash c fetch form : 200