Question

我想在没有迭代的情况下对哈希执行块操作，如下所示：

myhash = {
    foo: 'foo',
    bar: 'bar',
    baz: 'baz'
}

with myhash do 
   # operation with foo:
   # operation with bar:
   # other operations, etc
   # operation with baz:
end

避免语法重复：

myhash[:foo]
myhash[:bar]
myhash[:baz]
# much mo keys

这可能吗？

Answer 1

无法在Ruby中创建局部变量（1.9+）;所以你很难使用Hash，OpenStruct或Struct。（"Convert a Hash into a Struct"）只需使用Hash，这不是什么大不了的事。

Answer 2

虽然很多人认为坚持使用myhash[:foo]可能会更好，但它可以做你想做的事情，但仅限于科学！

require 'ostruct'

myhash = OpenStruct.new({
    foo: 'foo',
    bar: 'bar',
    baz: 'baz'
})

# you can do stuff like this with ostruct
myhash.foo
myhash.bar

@thing = "urgh"
thing = @thing

# every object has a built in tap method
myhash.tap { |h|
  p @thing
  h.foo + h.bar
}

# evey object has the instance_eval method
# when using instance eval, there are some trade-off
myhash.instance_eval do
  # instance variables don't work as you'd expect in there
  p @thing
  # but variables and methods do!
  p thing
  derp = 4
  p (foo * derp)
  p (baz + foo * derp)
end

很抱歉输出很乱，但你没有指定输出的样子：）

Answer 3

不确定它是否有用，我只会使用哈希语法，但你可以做类似

的事情

foo, bar, baz = myhash.values_at(:foo, :bar, :baz)

或将其转换为OpenStruct：

h = OpenStruct.new(myhash)

然后你就可以写

了

h.foo = h.bar + h.baz

Answer 4

你可以这样做：

my_dogs = { dog1: "Bobo", dog2: "Millie", dog3: "Billy-Bob", dog4: "Erma" }

flea_ridden = my_dogs.values_at(:dog3, :dog1, :dog4)
  #=> ["Billy-Bob", "Bobo", "Erma"] 
str = "My dogs "
  #=> "My dogs " 
str << "#{flea_ridden.shift}, "
  #=> "My dogs Billy-Bob, " 
str << "#{flea_ridden.shift}, "
  #=> "My dogs Billy-Bob, Bobo, " 
str << "and "
  #=> "My dogs Billy-Bob, Bobo, and " 
str << "#{flea_ridden.shift} "
  #=> "My dogs Billy-Bob, Bobo, and Erma " 
str << "have fleas"
  #=> "My dogs Billy-Bob, Bobo, and Erma have fleas" 
puts str
  # My dogs Billy-Bob, Bobo, and Erma have fleas

在哈希中执行操作

4 个答案: