{"id":8793,"date":"2011-12-27T07:00:00","date_gmt":"2011-12-27T07:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/2011\/12\/27\/introducing-the-for-if-anti-pattern\/"},"modified":"2011-12-27T07:00:00","modified_gmt":"2011-12-27T07:00:00","slug":"introducing-the-for-if-anti-pattern","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20111227-00\/?p=8793","title":{"rendered":"Introducing the for-if anti-pattern"},"content":{"rendered":"

\nOver the years, I’ve seen a bunch of coding anti-patterns.\nI figured maybe I’ll share a few.\n<\/p>\n

\nToday, I’ll introduce\nwhat I’m calling the for-if<\/i> anti-pattern,\nalso known as\n“We’ll sell you the whole seat, but you’ll only need the edge<\/a>.”\nThis is a special case of the for-case<\/i> anti-pattern, where\nall but one of the cases is null.\n<\/p>\n

\nfor (int i = 0; i < 100; i++) {\n  if (i == 42) { do_something(i); }\n}\n<\/pre>\n
\nThis can naturally be simplified to\n<\/p>\n
\ndo_something(42);\n<\/pre>\n
\nThe for-if<\/i> anti-pattern arises in many forms.\nFor example:\n<\/p>\n
\nforeach (string filename in Directory.GetFiles(\".\"))\n{\n    if (filename.Equals(\"desktop.ini\", StringComparison.OrdinalIgnoreCase<\/a>))\n    {\n        return new StreamReader(filename);\n    }\n}\n<\/pre>\n
\nThis enumerates all the files in a directory looking for a specific one,\nand if it’s found, it returns a stream on it.\nThe slightly-less-crazy version would be\n<\/p>\n
\nif (File.Exists(\"desktop.ini\"))\n{\n    return new StreamReader(\"desktop.ini\");\n}\n<\/pre>\n
\nNote that both versions of the code fragment have the same race condition:\nIf the file desktop.ini<\/code> initially exists but gets deleted\nbefore you get around to creating a new Stream­Reader<\/code>,\nyou will get a File­Not­Found­Exception<\/code>.\n<\/p>\n
\nOne final example:\n<\/p>\n
\nforeach (object o in hashtable.Keys)\n{\n    if (o == \"target\") return hashtable[\"target\"];\n}\n<\/pre>\n
\nAlso known as\n<\/p>\n
\nreturn hashtable[\"target\"];\n<\/pre>\n
\nI bet these people hate going to the library to get a book by title,\nbecause it takes so darn long:\nThey go up to the librarian and say,\n“Please give me all the books you have,”\nand then they fill up their cart with thousands of books,\nthen sit in the corner saying,\n“Nope, the title of this book is wrong.\nNope, not that one either.\nStill the wrong title.\nHow about this book?\nNope, not this one either.\nMan, this is taking forever<\/i>…”<\/p>\n","protected":false},"excerpt":{"rendered":"
Over the years, I’ve seen a bunch of coding anti-patterns. I figured maybe I’ll share a few. Today, I’ll introduce what I’m calling the for-if anti-pattern, also known as “We’ll sell you the whole seat, but you’ll only need the edge.” This is a special case of the for-case anti-pattern, where all but one of […]<\/p>\n","protected":false},"author":1069,"featured_media":111744,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[25],"class_list":["post-8793","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"
Over the years, I’ve seen a bunch of coding anti-patterns. I figured maybe I’ll share a few. Today, I’ll introduce what I’m calling the for-if anti-pattern, also known as “We’ll sell you the whole seat, but you’ll only need the edge.” This is a special case of the for-case anti-pattern, where all but one of […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/8793","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/users\/1069"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/comments?post=8793"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/8793\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media\/111744"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media?parent=8793"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=8793"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=8793"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}