{"id":99,"date":"2012-02-08T21:40:43","date_gmt":"2012-02-09T05:40:43","guid":{"rendered":"http:\/\/www.lorrin.org\/blog\/?p=99"},"modified":"2012-03-16T23:26:45","modified_gmt":"2012-03-17T06:26:45","slug":"how-to-treat-a-bare-value-as-an-array-in-ruby","status":"publish","type":"post","link":"https:\/\/www.lorrin.org\/blog\/2012\/02\/08\/how-to-treat-a-bare-value-as-an-array-in-ruby\/","title":{"rendered":"How to treat a bare value as an Array in Ruby"},"content":{"rendered":"

Often Array(arg)<\/code> is used for this, but is flawed. Note the last result when applied to a Hash:<\/p>\n

> Array(42)\r\n\u00a0=> [42] \r\n> Array([1,2,3])\r\n\u00a0=> [1, 2, 3] \r\n> Array(nil)\r\n\u00a0=> [] \r\n> Array(\"foo\")\r\n\u00a0=> [\"foo\"] \r\n> Array({\"foo\" => \"bar\", \"biz\" => \"baz\"})\r\n\u00a0=> [[\"foo\", \"bar\"], [\"biz\", \"baz\"]]<\/pre>\n
What went wrong is that Array() calls the (now deprecated) to_a<\/code> on each of its arguments. Hash has a custom to_a<\/code> implementation with different semantics. Instead, do\u00a0 this:<\/p>\n
class Array\r\n\u00a0 def self.wrap(args)\r\n\u00a0\u00a0\u00a0 return [] unless args\r\n\u00a0\u00a0\u00a0 args.is_a?(Array) ? args : [args]\r\n\u00a0 end\r\nend<\/pre>\n
That yields the expected results, even for Hashes:<\/p>\n
> Array.wrap(42)\r\n\u00a0=> [42] \r\n> Array.wrap([1,2,3])\r\n\u00a0=> [1, 2, 3] \r\n> Array.wrap(nil)\r\n\u00a0=> [] \r\n> Array.wrap(\"foo\")\r\n\u00a0=> [\"foo\"] \r\n> Array.wrap({\"foo\" => \"bar\", \"biz\" => \"baz\"})\r\n\u00a0=> [{\"foo\"=>\"bar\", \"biz\"=>\"baz\"}]<\/pre>\n
Use of is_a?<\/code> is deliberate; duck-typing in this situation ([:[], :each].all? { |m| args.respond_to? m }<\/code>) yields unexpected surprises since e.g. String is Enumerable and would not get wrapped.<\/p>\n
For further discussion see Ruby-forum thread “shortcut for x = [x] unless x.is_a?(Array)<\/a>” and StackOverflow “Ruby: Object.to_a replacement<\/a>“.<\/p>\n","protected":false},"excerpt":{"rendered":"
Often Array(arg) is used for this, but is flawed. Note the last result when applied to a Hash: > Array(42) \u00a0=> [42] > Array([1,2,3]) \u00a0=> [1, 2, 3] > Array(nil) \u00a0=> [] > Array(“foo”) \u00a0=> [“foo”] > Array({“foo” => “bar”, “biz” => “baz”}) \u00a0=> [[“foo”, “bar”], [“biz”, “baz”]] What went wrong is that Array() calls […]<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[48],"tags":[31],"_links":{"self":[{"href":"https:\/\/www.lorrin.org\/blog\/wp-json\/wp\/v2\/posts\/99"}],"collection":[{"href":"https:\/\/www.lorrin.org\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lorrin.org\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lorrin.org\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lorrin.org\/blog\/wp-json\/wp\/v2\/comments?post=99"}],"version-history":[{"count":4,"href":"https:\/\/www.lorrin.org\/blog\/wp-json\/wp\/v2\/posts\/99\/revisions"}],"predecessor-version":[{"id":154,"href":"https:\/\/www.lorrin.org\/blog\/wp-json\/wp\/v2\/posts\/99\/revisions\/154"}],"wp:attachment":[{"href":"https:\/\/www.lorrin.org\/blog\/wp-json\/wp\/v2\/media?parent=99"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lorrin.org\/blog\/wp-json\/wp\/v2\/categories?post=99"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lorrin.org\/blog\/wp-json\/wp\/v2\/tags?post=99"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}