为什么拆分字符串不一致？

Question

Examine:

"test.one.two".split(".") # => ["test", "one", "two"]

Right, perfect. Exactly what we want.

"test..two".split(".") # => ["test", "", "two"]

I replaced one with the empty string, so that makes sense

"test".split(".") # => ["test"]

That's what I would expect, no problems here.

".test".split(".") # => ["", "test"]

Yep, my string has one . so I got two sections as a result.

"test.".split(".") # => ["test"]

What? There's a . in my string, it should have been split into two sections. I didn't ask to get rid of empty strings; it didn't get rid of empty strings back in tests 2 or 4.
I would have expected ["test", ""]

"".split(".") # => []

WHAT? This should operate almost exactly like test 3, and return [""] . But now I can't perform any string methods on result[0]

Why is this inconsistent for splits that occur on the edges, or for the empty string?

Answer 1

The documentation explains this well: http://ruby-doc.org/core-2.2.0/String.html#method-i-split

If the limit parameter is omitted, trailing null fields are suppressed. If limit is a positive number, at most that number of fields will be returned (if limit is 1, the entire string is returned as the only entry in an array). If negative, there is no limit to the number of fields returned, and trailing null fields are not suppressed.

So, this does what you'd expect:

"test.".split(".", -1)
 => ["test", ""]

The rest is there in the docs.