burke / andand2 Goto Github PK

It looks like you meant for the .andand method chain to return nil when a method does not exist, but that is not the case. It returns and AndAnd wrapper object. This means you can't use .andand naked on conditional statement. You must compare the result of the method chain to something, and that something can't be nil, since that is not what .andand returns.

rb(main):037:0> x = "".andand.foo
=> nil
irb(main):038:0> x
=> nil
irb(main):039:0> x ? 1 : 2
=> 1
irb(main):040:0> nil ? 1 : 2
=> 2
irb(main):041:0> nil == x
=> false

The problem is that a .andand method chain with a missing method never returns nil. It only ever returns another AndAnd wrapper object. Ruby internally checks whether the value of a condition is nil when evaluating the truth of the condition. And since AndAnd objects are not nil, then the condition is never false.

Also, storing internally nil in @@and_and_nil and then overriding the instance's method_missing method is both unnecessary and dangerous. Its unnecessary because nil is a singleton, thus you can always refer the single instance with nil and @@and_and_nil is never actually returned. And its dangerous because you are overriding method_missing in the singleton.

irb(main):001:0> require 'andand2'
=> true
irb(main):002:0> nil.foo
=> nil

The problem with not returning nil can probably be solved by adding an .andend method to Object bookend the method chain. If the method is invoked on an AndAnd instance, then it would return nil, otherwise it would return self.

Thus "".andand.foo.andend would return nil, whereas "ABC".andand.downcase.andend would return abc.