Conditional inserts in inject

[David Heinemeier Hansson]

Consider:

%w{ one two three }.inject(Array.new) { |a, e| a << e if e != "three" }

I would have expected that to return:

[ "one", "two" ]

Instead it returns nil.

What am I missing? Or isn't it possible to use conditions in an inject
expression? If not, how would one go about archiving the same?


/ David

 

[ts]

D> %w{ one two three }.inject(Array.new) { |a, e| a << e if e != "three" }
^^^^^^^^^^^^^^^^^^^^^^

this is the same than

if e != "three"
a << e
else
nil
end

this is why it return nil


Guy Decoux

 

[Dan Doel]

%w{ one two three }.inject(Array.new) { |a, e| if e != "three" then a <<
e else a end }

The value of the block is assigned to a in the next iteration, or
returned if it's the last
iteration, so you need to return the array itself if you're doing nothing.