Ruby Array uniq
List post
post_a (topic_name: "Ruby", priority: 10)
post_b (topic_name: "PHP", priority: 9)
post_c (topic_name: "Ruby", priority: 8)
Expect each topic has only 1 post, order by priority
current_posts
# => [["Ruby", post_a], ["PHP", post_b], ["Ruby", post_c]]
to_h
current_posts.to_h
# => {"Ruby" => post_c, "PHP" => post_b}
=> post_c with lower priority is above post_b => ERROR
uniq
current_posts.uniq(&:first).to_h
# => {"Ruby" => post_a, "PHP" => post_b}
=> as expected