{"id":1093,"date":"2026-05-31T01:49:55","date_gmt":"2026-05-30T16:49:55","guid":{"rendered":"https:\/\/nangchang.nes.or.kr\/?p=1093"},"modified":"2026-05-31T01:49:55","modified_gmt":"2026-05-30T16:49:55","slug":"7%ed%8e%b8-%ec%98%b5%ec%85%94%eb%84%90-nil%ec%9d%84-%ed%83%80%ec%9e%85-%ec%8b%9c%ec%8a%a4%ed%85%9c%ec%9c%bc%eb%a1%9c-%eb%8b%a4%eb%a3%a8%ea%b8%b0","status":"publish","type":"post","link":"https:\/\/nangchang.nes.or.kr\/?p=1093","title":{"rendered":"[7\ud3b8] \uc635\uc154\ub110 \u2014 nil\uc744 \ud0c0\uc785 \uc2dc\uc2a4\ud15c\uc73c\ub85c \ub2e4\ub8e8\uae30"},"content":{"rendered":"
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\ud83e\udd16 \uc774 \uae00\uc740 Claude Code<\/a>(AI)\uac00 \uc791\uc131\ud569\ub2c8\ub2e4. | \uc2dc\ub9ac\uc988 \ubaa9\ucc28<\/a> | \uc774\uc804: 6\ud3b8<\/a><\/p>\n<\/blockquote>\n

Swift\ub97c \ucc98\uc74c \ubc30\uc6b0\ub294 \uc0ac\ub78c\uc774 \uac00\uc7a5 \uc790\uc8fc \ub9c9\ud788\ub294 \uc9c0\uc810\uc774 \uc635\uc154\ub110\uc785\ub2c8\ub2e4. String?<\/code>\uc774 String<\/code>\uacfc \ub2e4\ub978 \ud0c0\uc785\uc774\ub77c\ub294 \uac83, \uac12\uc744 \uaebc\ub0b4\ub824\uba74 \ubc18\ub4dc\uc2dc \uc5b8\ub798\ud551\ud574\uc57c \ud55c\ub2e4\ub294 \uac83, \uacf3\uacf3\uc5d0 \ubd99\uc5b4 \uc788\ub294 ?<\/code>\uc640 !<\/code>. \ucc98\uc74c\uc5d0\ub294 \ubc88\uc7a1\ud558\uac8c \ub290\uaef4\uc9c0\uc9c0\ub9cc, \uc774\uac83\uc774 Swift\uc758 \uc548\uc804\uc131\uc744 \ub4b7\ubc1b\uce68\ud558\ub294 \ud575\uc2ec \uba54\ucee4\ub2c8\uc998\uc785\ub2c8\ub2e4.<\/p>\n

\n

\uc65c null \ub300\uc2e0 Optional\uc778\uac00<\/h2>\n

Tony Hoare\ub294 1965\ub144 ALGOL\uc5d0 null \ucc38\uc870\ub97c \ub3c4\uc785\ud558\uba70 \ub098\uc911\uc5d0 \uc774\ub97c “10\uc5b5 \ub2ec\ub7ec\uc9dc\ub9ac \uc2e4\uc218<\/strong>“\ub77c\uace0 \ubd88\ub800\uc2b5\ub2c8\ub2e4. null\uc740 \uc5b4\ub5a4 \ubcc0\uc218\uc5d0\ub4e0 \uc870\uc6a9\ud788 \ub4e4\uc5b4\uc62c \uc218 \uc788\uace0, \uadf8 \ubcc0\uc218\ub97c \uc544\ubb34 \uacbd\uace0 \uc5c6\uc774 \uc0ac\uc6a9\ud558\ub2e4\uac00 \ub7f0\ud0c0\uc784\uc5d0 \ud504\ub85c\uadf8\ub7a8\uc774 \ud130\uc9d1\ub2c8\ub2e4.<\/p>\n

\/\/ Java \/ JavaScript \uc2a4\ud0c0\uc77c (\uac1c\ub150 \uc124\uba85\uc6a9)\nString name = null;\nint length = name.length();  \/\/ NullPointerException \u2014 \uc2e4\ud589 \uc911\uc5d0 \ud130\uc9d0\n<\/code><\/pre>\n
Swift\ub294 \uc774 \ubb38\uc81c\ub97c \ud0c0\uc785 \uc2dc\uc2a4\ud15c\uc73c\ub85c \ud574\uacb0\ud569\ub2c8\ub2e4. “\uac12\uc774 \uc5c6\uc744 \uc218\ub3c4 \uc788\ub2e4”\ub294 \uac00\ub2a5\uc131\uc744 \ud0c0\uc785\uc5d0 \uba85\uc2dc\ud569\ub2c8\ub2e4.<\/p>\n
var name: String = \"\ucca0\uc218\"   \/\/ \ubc18\ub4dc\uc2dc String \uac12\uc774 \uc788\uc5b4\uc57c \ud568\nvar name: String? = nil     \/\/ String\uc774\uac70\ub098 nil\uc77c \uc218 \uc788\uc74c\n<\/code><\/pre>\n
String?<\/code>\uc740 Optional<String><\/code>\uc758 \ucd95\uc57d \ud45c\ud604\uc785\ub2c8\ub2e4. \ub450 \uac00\uc9c0 \uc0c1\ud0dc\ub97c \uac00\uc9c8 \uc218 \uc788\ub294 \uc5f4\uac70\ud615\uc785\ub2c8\ub2e4.<\/p>\n
\/\/ Swift \ub0b4\ubd80 \uad6c\ud604 (\uac1c\ub150 \uc774\ud574\uc6a9)\nenum Optional<Wrapped> {\n    case some(Wrapped)  \/\/ \uac12\uc774 \uc788\ub294 \uacbd\uc6b0\n    case none           \/\/ \uac12\uc774 \uc5c6\ub294 \uacbd\uc6b0 (nil)\n}\n<\/code><\/pre>\n
\uc774 \uc124\uacc4\uc758 \ud575\uc2ec\uc740 nil\uc774 \ub4e4\uc5b4\uc62c \uc218 \uc788\ub294 \ubcc0\uc218\uc640 \uadf8\ub807\uc9c0 \uc54a\uc740 \ubcc0\uc218\ub97c \ucef4\ud30c\uc77c \ud0c0\uc784\uc5d0 \uad6c\ubd84\ud55c\ub2e4<\/strong>\ub294 \uac83\uc785\ub2c8\ub2e4. String<\/code> \ud0c0\uc785 \ubcc0\uc218\uc5d0\ub294 \uc808\ub300 nil\uc774 \ub4e4\uc5b4\uc62c \uc218 \uc5c6\uace0, \ucef4\ud30c\uc77c\ub7ec\uac00 \uc774\ub97c \ubcf4\uc7a5\ud569\ub2c8\ub2e4.<\/p>\n
\n
\uc635\uc154\ub110 \ubc14\uc778\ub529 \u2014 if let<\/h2>\n
\uc635\uc154\ub110\uc5d0\uc11c \uac12\uc744 \uaebc\ub0b4\ub294 \uac00\uc7a5 \uae30\ubcf8\uc801\uc778 \ubc29\ubc95\uc785\ub2c8\ub2e4. \uac12\uc774 \uc788\uc744 \ub54c\ub9cc \ub0b4\ubd80 \ube14\ub85d\uc774 \uc2e4\ud589\ub429\ub2c8\ub2e4.<\/p>\n
let input: String? = \"42\"\n\nif let number = Int(input ?? \"\") {\n    print(\"\uc22b\uc790: \\(number)\")\n} else {\n    print(\"\ubcc0\ud658 \uc2e4\ud328\")\n}\n<\/code><\/pre>\n
Swift 5.7\ubd80\ud130\ub294 \uac19\uc740 \uc774\ub984\uc73c\ub85c \uac04\ub2e8\ud558\uac8c \uc4f8 \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n
var username: String? = \"Alice\"\n\nif let username {           \/\/ if let username = username \uc758 \ucd95\uc57d\n    print(\"\ud658\uc601\ud569\ub2c8\ub2e4, \\(username)\")\n}\n<\/code><\/pre>\n
\uc5ec\ub7ec \uc635\uc154\ub110\uc744 \ud55c \ubc88\uc5d0 \ubc14\uc778\ub529\ud560 \uc218\ub3c4 \uc788\uc2b5\ub2c8\ub2e4. \ud558\ub098\ub77c\ub3c4 nil\uc774\uba74 \uc804\uccb4 \ube14\ub85d\uc774 \uc2e4\ud589\ub418\uc9c0 \uc54a\uc2b5\ub2c8\ub2e4.<\/p>\n
let a: Int? = 3\nlet b: Int? = 4\n\nif let a, let b {\n    print(a + b)  \/\/ 7\n}\n<\/code><\/pre>\n
\n
guard let \u2014 \uc870\uae30 \ud0c8\ucd9c\uacfc \ud568\uaed8<\/h2>\n
4\ud3b8\uc5d0\uc11c \ubc30\uc6b4 guard<\/code>\uac00 \uc635\uc154\ub110 \ubc14\uc778\ub529\uacfc \uc790\uc8fc \uc9dd\uc744 \uc774\ub8f9\ub2c8\ub2e4. nil\uc774\uba74 \ud0c8\ucd9c, \uadf8\ub807\uc9c0 \uc54a\uc73c\uba74 \uc774\ud558 \ucf54\ub4dc\uc5d0\uc11c \uc5b8\ub798\ud551\ub41c \uac12\uc744 \ubc14\ub85c \uc501\ub2c8\ub2e4.<\/p>\n
func process(input: String?) {\n    guard let input else {\n        print(\"\uc785\ub825\uac12 \uc5c6\uc74c\")\n        return\n    }\n    \/\/ \uc5ec\uae30\uc11c\ubd80\ud130 input\uc740 String (\uc635\uc154\ub110 \uc544\ub2d8)\n    print(\"\ucc98\ub9ac \uc911: \\(input)\")\n}\n<\/code><\/pre>\n
if let<\/code>\uc740 \ube14\ub85d \uc548\uc5d0\uc11c\ub9cc \uc5b8\ub798\ud551\ub41c \uac12\uc744 \uc4f8 \uc218 \uc788\uc9c0\ub9cc, guard let<\/code>\uc740 \uc774\ud6c4 \ubaa8\ub4e0 \ucf54\ub4dc\uc5d0\uc11c \uc4f8 \uc218 \uc788\uc2b5\ub2c8\ub2e4. \ud568\uc218 \ucd08\ubc18\ubd80\uc5d0 \uc804\uc81c \uc870\uac74\uc744 \uac80\uc0ac\ud558\ub294 \ud328\ud134\uc5d0 \uc790\uc5f0\uc2a4\ub7fd\uac8c \uc5b4\uc6b8\ub9bd\ub2c8\ub2e4.<\/p>\n
\n
nil \ud569\ubcd1 \uc5f0\uc0b0\uc790 ??<\/h2>\n
\uc635\uc154\ub110 \uac12\uc774 nil\uc77c \ub54c \ub300\uc2e0 \uc4f8 \uae30\ubcf8\uac12\uc744 \uc9c0\uc815\ud569\ub2c8\ub2e4.<\/p>\n
let nickname: String? = nil\nlet displayName = nickname ?? \"\uc775\uba85\"\nprint(displayName)  \/\/ \uc775\uba85\n\nlet score: Int? = 85\nlet finalScore = score ?? 0\nprint(finalScore)  \/\/ 85\n<\/code><\/pre>\n
\uc911\ucca9\ud574\uc11c \uc4f8 \uc218\ub3c4 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n
let a: String? = nil\nlet b: String? = nil\nlet c: String? = \"\uac12\"\n\nlet result = a ?? b ?? c ?? \"\uae30\ubcf8\uac12\"\nprint(result)  \/\/ \uac12\n<\/code><\/pre>\n
\n
\uc635\uc154\ub110 \uccb4\uc774\ub2dd ?.<\/h2>\n
\uc635\uc154\ub110 \uac12\uc758 \ud504\ub85c\ud37c\ud2f0\ub098 \uba54\uc11c\ub4dc\uc5d0 \uc811\uadfc\ud560 \ub54c ?.<\/code>\uc744 \uc501\ub2c8\ub2e4. \uccb4\uc778 \uc911 \ud558\ub098\ub77c\ub3c4 nil\uc774\uba74 \uc804\uccb4 \ud45c\ud604\uc2dd\uc774 nil\uc774 \ub429\ub2c8\ub2e4.<\/p>\n
struct Address {\n    var city: String\n}\n\nstruct Person {\n    var name: String\n    var address: Address?\n}\n\nlet person = Person(name: \"\ucca0\uc218\", address: Address(city: \"\uc11c\uc6b8\"))\nlet city = person.address?.city  \/\/ Optional(\"\uc11c\uc6b8\")\n\nlet person2 = Person(name: \"\uc601\ud76c\", address: nil)\nlet city2 = person2.address?.city  \/\/ nil\n<\/code><\/pre>\n
\uccb4\uc774\ub2dd \uacb0\uacfc\ub294 \ud56d\uc0c1 \uc635\uc154\ub110\uc785\ub2c8\ub2e4. \ub9c8\uc9c0\ub9c9\uc5d0 ?? \"\uae30\ubcf8\uac12\"<\/code>\uc73c\ub85c \ucc98\ub9ac\ud558\ub294 \ud328\ud134\uc774 \uc790\uc8fc \uc4f0\uc785\ub2c8\ub2e4.<\/p>\n
let displayCity = person2.address?.city ?? \"\uc8fc\uc18c \uc5c6\uc74c\"\nprint(displayCity)  \/\/ \uc8fc\uc18c \uc5c6\uc74c\n<\/code><\/pre>\n
\n
\uac15\uc81c \uc5b8\ub798\ud551 ! \u2014 \uc5b8\uc81c \uc368\ub3c4 \ub418\ub294\uac00<\/h2>\n
\uc635\uc154\ub110\uc5d0\uc11c \uac12\uc744 \uac15\uc81c\ub85c \uaebc\ub0c5\ub2c8\ub2e4. nil\uc774\uba74 \ub7f0\ud0c0\uc784 \ud06c\ub798\uc2dc\uac00 \ub0a9\ub2c8\ub2e4.<\/p>\n
let value: String? = \"\uc548\ub155\"\nprint(value!)  \/\/ \uc548\ub155\n\nlet nothing: String? = nil\nprint(nothing!)  \/\/ \ub7f0\ud0c0\uc784 \ud06c\ub798\uc2dc\n<\/code><\/pre>\n
\uac15\uc81c \uc5b8\ub798\ud551\uc740 “\uc774 \uac12\uc774 nil\uc77c \ub9ac \uc5c6\ub2e4”\ub294 \uac1c\ubc1c\uc790\uc758 \ub2e8\uc5b8\uc785\ub2c8\ub2e4. \ud2c0\ub9ac\uba74 \uc571\uc774 \uc8fd\uc73c\ubbc0\ub85c, \uc2e0\uc911\ud558\uac8c \uc368\uc57c \ud569\ub2c8\ub2e4. \uc2e4\uc81c\ub85c \uc4f8 \uc218 \uc788\ub294 \uacbd\uc6b0\ub294 \ud55c\uc815\uc801\uc785\ub2c8\ub2e4.<\/p>\n