somearray = ["some", "thing"]
anotherarray = ["another", "thing"]
somearray.push(anotherarray.flatten!)
期待したのは
["some","thing","another","thing"]
演算子「+」を使えばいいのです。
irb(main):001:0> a = [1,2]
=> [1, 2]
irb(main):002:0> b = [3,4]
=> [3, 4]
irb(main):003:0> a + b
=> [1, 2, 3, 4]
配列クラスについての詳細はこちらをご覧ください。 http://ruby-doc.org/core/classes/Array.html