Ruby：使用键/值数组设置新哈希

Question

(--工作人员删除的问题--)

Answer 1

Is this an example of the difference between class methods and instance methods?

Exactly.

But why can this be shortened to just Hash[*order] ?

Ruby interprets some_object[] as a call to the method named [] on some_object . This isn't special for Hashes, you can implement a [] method in any class of your own and use that syntax.

Can someone explain what's going on here, and if there are alternate ways to add values from an array into a hash?

Hash[*order] calls a class method ( Hash#[] ) which creates a new Hash. o.[](*order) doesn't work for the same reason you can't call new on it: {}.new doesn't make any sense. You can't call a class method on an instance of the class.

You can add values with merge :

o = Hash.new
o.merge(Hash[*order])

o = {*order} doesn't work because {} is the syntax for a Hash literal, and putting *order in there doesn't make sense.

Hash(*order) is Kernel#Hash , a method that expects only one argument.

Answer 2

When you write Hash(*order) you're actually calling the Hash method in the Kernel module, which is not the same as calling the [] method in the Hash class. See the docs for Kernel#Hash to see what's going on under the hood there.