ruby not understanding this behavior when iterating through array

Question

I am having a problem with the following array iteration. I'd like to create an array jt with the phrase "food" and "drink" as can be seen from the output from first command which is constructed from an item that has two global_tags with each tag having a phrase that is, in this case, food or drink. I'm not sure why I get the two embedded arrays as seen in the last line.

1.9.3p392 :043 > m.global_tags.map { |t| puts t.tag.phrase }
drink
food
 => [nil, nil] 
1.9.3p392 :044 > jt=[]
 => [] 
1.9.3p392 :045 > m.global_tags.map { |t| jt << t.tag.phrase }
 => [["drink", "food"], ["drink", "food"]] 
1.9.3p392 :046 >

Also, I'm trying to get shorter syntax. This seems to work but not sure if this is considered ugly in Ruby terms(?)

1.9.3p392 :050 > m.global_tags.map(&:tag).map(&:phrase)
 => ["drink", "food"]

Thx for help

I don't think the latter is ugly, as long as you understand it and it doesn't get too convoluted it's fine. — squiguy
– squiguy, Commented May 22, 2013 at 20:10

Ven · Accepted Answer · 2013-05-22 20:05:57Z

2

You get two embedded arrays as the return value from .map, it's not jt. If you only need side-effects, use .each
This is bad performance-wise because you have to traverse the array two times.

m.global_tags.map { |t| t.tag.phrase } returns the result you want.

answered May 22, 2013 at 20:05

Ven

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2 Comments

timpone Over a year ago

thx, yeah 1 is right - my mistake. Think I was trying to do something like your suggestion. have to wait like 10 min.

Ven Over a year ago

np - glad to know I helped anyway :)

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