File.join compared with Pathname#join

[Walter Lee Davis]

This difference was surprising to me:

irb (2.4.4)
require ‘pathname’
Pathname.new(‘foo’).join(‘/bar’)
=> #<Pathname:/bar>
Pathname.new(‘foo’).join(‘bar’)
=> #<Pathname:foo/bar>

File.join(‘foo’, ‘/bar’)
=> “foo/bar”
File.join(‘foo’, ‘bar’)
=> “foo/bar”

Is there a reasonable explanation that I can’t think of for this behavior?

Walter

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[botp]

​that is fine.
​

Post by Walter Lee Davis
irb (2.4.4)
require ‘pathname’
Pathname.new(‘foo’).join(‘/bar’)
=> #<Pathname:/bar>

​when you join an absolute path, it overrides (unjoins) all other existing
paths​ and makes it the new base path.

Post by Walter Lee Davis
Pathname.new("foo").join("/bar").join("baz")

=> #<Pathname:/bar/baz>

​> Pathname.new("foo").join("/bar").join("/ruby")
=> #<Pathname:/ruby>
​

Pathname.new(‘foo’).join(‘bar’)

Post by Walter Lee Davis
=> #<Pathname:foo/bar>

​ok

​

Post by Walter Lee Davis
File.join(‘foo’, ‘/bar’)
=> “foo/bar”
File.join(‘foo’, ‘bar’)
=> “foo/bar”

​File is very basic; just treats them as string w the file separator (yet
discards separator if you prepend one : ) Since file returns string
chaining fails thereafter,

Post by Walter Lee Davis
File.join("bar","foo").join("ruby")

NoMethodError: undefined method `join' for "bar/foo":String

Post by Walter Lee Davis
Is there a reasonable explanation that I can’t think of for this behavior?

​i think ruby doc is not so clear on this behaviour (havent check current
yet), but
this is common in other languages (eg python) or on other platforms​

Post by Walter Lee Davis
Walter