{"id":1090,"date":"2026-05-31T01:46:50","date_gmt":"2026-05-30T16:46:50","guid":{"rendered":"https:\/\/nangchang.nes.or.kr\/?p=1090"},"modified":"2026-05-31T01:46:50","modified_gmt":"2026-05-30T16:46:50","slug":"4%ed%8e%b8-%ec%a0%9c%ec%96%b4-%ed%9d%90%eb%a6%84-if-switch-guard-for-while","status":"publish","type":"post","link":"https:\/\/nangchang.nes.or.kr\/?p=1090","title":{"rendered":"[4\ud3b8] \uc81c\uc5b4 \ud750\ub984 \u2014 if, switch, guard, for, while"},"content":{"rendered":"
\n

\ud83e\udd16 \uc774 \uae00\uc740 Claude Code<\/a>(AI)\uac00 \uc791\uc131\ud569\ub2c8\ub2e4. | \uc2dc\ub9ac\uc988 \ubaa9\ucc28<\/a> | \uc774\uc804: 3\ud3b8<\/a><\/p>\n<\/blockquote>\n

\uc81c\uc5b4 \ud750\ub984\uc740 \uc5b4\ub5a4 \uc5b8\uc5b4\uc5d0\uc11c\ub098 \ube44\uc2b7\ud574 \ubcf4\uc785\ub2c8\ub2e4. if<\/code>\ub85c \ubd84\uae30\ud558\uace0, \ubc18\ubcf5\ubb38\uc73c\ub85c \ub3cc\ub9ac\uace0. \ud558\uc9c0\ub9cc Swift\uc5d0\ub294 \ub2e4\ub978 \uc5b8\uc5b4\uc640 \ud655\uc5f0\ud788 \ub2e4\ub978 \ub450 \uac00\uc9c0\uac00 \uc788\uc2b5\ub2c8\ub2e4. switch<\/code>\uc758 \uc791\ub3d9 \ubc29\uc2dd\uacfc guard<\/code>\ub77c\ub294 \ud0a4\uc6cc\ub4dc\uc785\ub2c8\ub2e4. \uc774 \ub450 \uac00\uc9c0\ub97c \uc911\uc2ec\uc73c\ub85c Swift\uc758 \uc81c\uc5b4 \ud750\ub984\uc744 \uc0b4\ud3b4\ubd05\ub2c8\ub2e4.<\/p>\n

\n

if \/ else if \/ else<\/h2>\n

\uae30\ubcf8 \uad6c\uc870\ub294 \ub2e4\ub978 \uc5b8\uc5b4\uc640 \uac19\uc2b5\ub2c8\ub2e4. \ud55c \uac00\uc9c0 \ucc28\uc774\ub294 \uc870\uac74\uc2dd\uc744 \uad04\ud638\ub85c \uac10\uc300 \ud544\uc694\uac00 \uc5c6\ub2e4\ub294 \uac83\uc785\ub2c8\ub2e4(\uac10\uc2f8\ub3c4 \ub418\uc9c0\ub9cc Swift \uad00\ub840\ub294 \uc0dd\ub7b5).<\/p>\n

let temperature = 22\n\nif temperature > 30 {\n    print(\"\ub365\ub2e4\")\n} else if temperature > 20 {\n    print(\"\ucf8c\uc801\ud558\ub2e4\")\n} else {\n    print(\"\ucda5\ub2e4\")\n}\n\/\/ \ucf8c\uc801\ud558\ub2e4\n<\/code><\/pre>\n
Swift\uc758 if<\/code>\ub294 \ubc18\ub4dc\uc2dc Bool<\/code> \uc870\uac74\ub9cc \ubc1b\uc2b5\ub2c8\ub2e4. 2\ud3b8\uc5d0\uc11c \uc5b8\uae09\ud588\ub4ef 0<\/code>\uc774\ub098 \ube48 \ubb38\uc790\uc5f4 \uac19\uc740 “\uac70\uc9d3 \uac19\uc740 \uac12(falsy)”\uc744 \uc554\ubb35\uc801\uc73c\ub85c \ucc98\ub9ac\ud558\uc9c0 \uc54a\uc2b5\ub2c8\ub2e4.<\/p>\n
let count = 0\nif count {          \/\/ \uc624\ub958: Bool\uc774 \uc544\ub2d8\n    print(\"empty\")\n}\nif count == 0 {     \/\/ \uc62c\ubc14\ub978 \ubc29\uc2dd\n    print(\"empty\")\n}\n<\/code><\/pre>\n
\n
switch \u2014 fallthrough \uc5c6\ub294 \ud328\ud134 \ub9e4\uce6d<\/h2>\n
Swift\uc758 switch<\/code>\ub294 C, Java, JavaScript\uc758 \uac83\uacfc \ud06c\uac8c \ub2e4\ub985\ub2c8\ub2e4. \ucc28\uc774\uc810\uc744 \uba3c\uc800 \ub098\uc5f4\ud558\uba74:<\/p>\n
    \n
  • fallthrough\uac00 \uae30\ubcf8\uc801\uc73c\ub85c \uc5c6\ub2e4<\/strong> \u2014 \uac01 case<\/code>\uac00 \ub05d\ub098\uba74 \uc790\ub3d9\uc73c\ub85c switch<\/code>\ub97c \ube60\uc838\ub098\uc628\ub2e4<\/li>\n
  • \ubaa8\ub4e0 \uacbd\uc6b0\ub97c \ubc18\ub4dc\uc2dc \ucc98\ub9ac\ud574\uc57c \ud55c\ub2e4<\/strong> \u2014 default<\/code>\ub85c \ub098\uba38\uc9c0\ub97c \ucc98\ub9ac\ud558\uac70\ub098, \uac00\ub2a5\ud55c \ubaa8\ub4e0 \ucf00\uc774\uc2a4\ub97c \uba85\uc2dc\ud574\uc57c \ud55c\ub2e4<\/li>\n
  • \ud328\ud134 \ub9e4\uce6d\uc744 \uc9c0\uc6d0\ud55c\ub2e4<\/strong> \u2014 \ub2e8\uc21c \uac12 \ube44\uad50\ub97c \ub118\uc5b4 \ubc94\uc704, \ud29c\ud50c, \ud0c0\uc785\uae4c\uc9c0 \ub9e4\uce6d\ud560 \uc218 \uc788\ub2e4<\/li>\n<\/ul>\n
    let score = 85\n\nswitch score {\ncase 90...100:\n    print(\"A\")\ncase 80..<90:\n    print(\"B\")\ncase 70..<80:\n    print(\"C\")\ndefault:\n    print(\"F\")\n}\n\/\/ B\n<\/code><\/pre>\n
    90...100<\/code>\uc740 90 \uc774\uc0c1 100 \uc774\ud558(\ub2eb\ud78c \ubc94\uc704), 80..<90<\/code>\uc740 80 \uc774\uc0c1 90 \ubbf8\ub9cc(\ubc18\uc5f4\ub9b0 \ubc94\uc704)\uc785\ub2c8\ub2e4.<\/p>\n
    \uc5ec\ub7ec \uac12\uc744 \ud55c \ucf00\uc774\uc2a4\uc5d0 \ubb36\uc744 \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n
    let day = \"\ud1a0\"\n\nswitch day {\ncase \"\ud1a0\", \"\uc77c\":\n    print(\"\uc8fc\ub9d0\")\ncase \"\uc6d4\", \"\ud654\", \"\uc218\", \"\ubaa9\", \"\uae08\":\n    print(\"\ud3c9\uc77c\")\ndefault:\n    print(\"\uc54c \uc218 \uc5c6\uc74c\")\n}\n<\/code><\/pre>\n
    where<\/code>\ub85c \ucd94\uac00 \uc870\uac74\uc744 \ubd99\uc77c \uc218\ub3c4 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n
    let point = (3, -2)\n\nswitch point {\ncase (0, 0):\n    print(\"\uc6d0\uc810\")\ncase (let x, 0):\n    print(\"x\ucd95 \uc704: \\(x)\")\ncase (0, let y):\n    print(\"y\ucd95 \uc704: \\(y)\")\ncase (let x, let y) where x == y:\n    print(\"y=x \uc120 \uc704\")\ncase (let x, let y):\n    print(\"(\\(x), \\(y))\")\n}\n\/\/ (3, -2)\n<\/code><\/pre>\n
    C \uc5b8\uc5b4 \uc2a4\ud0c0\uc77c\ucc98\ub7fc \uc758\ub3c4\uc801\uc73c\ub85c \ub2e4\uc74c \ucf00\uc774\uc2a4\ub85c \ud758\ub7ec\uac00\uac8c \ud558\uace0 \uc2f6\ub2e4\uba74 fallthrough<\/code> \ud0a4\uc6cc\ub4dc\ub97c \uba85\uc2dc\uc801\uc73c\ub85c \uc501\ub2c8\ub2e4. \ud558\uc9c0\ub9cc \uc2e4\uc81c\ub85c \uc4f8 \uc77c\uc740 \uac70\uc758 \uc5c6\uc2b5\ub2c8\ub2e4.<\/p>\n
    \n
    for-in<\/h2>\n
    3\ud3b8\uc5d0\uc11c \uceec\ub809\uc158 \uc21c\ud68c\uc5d0 \uc37c\ub358 \uac83\uacfc \uac19\uc2b5\ub2c8\ub2e4. \uc22b\uc790 \ubc94\uc704\uc5d0\ub3c4 \uc4f8 \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n
    for i in 1...5 {\n    print(i)  \/\/ 1, 2, 3, 4, 5\n}\n\nfor i in 1..<5 {\n    print(i)  \/\/ 1, 2, 3, 4\n}\n<\/code><\/pre>\n
    \ubc18\ubcf5 \ubcc0\uc218\uac00 \ud544\uc694 \uc5c6\uc744 \ub54c\ub294 _<\/code>\ub85c \ubb34\uc2dc\ud569\ub2c8\ub2e4.<\/p>\n
    for _ in 1...3 {\n    print(\"\ubc18\ubcf5\")\n}\n<\/code><\/pre>\n
    stride<\/code>\ub85c \uc99d\uac10 \ud3ed\uc744 \uc9c0\uc815\ud560 \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n
    for i in stride(from: 0, to: 10, by: 2) {\n    print(i)  \/\/ 0, 2, 4, 6, 8\n}\n<\/code><\/pre>\n
    \n
    while \/ repeat-while<\/h2>\n
    \uc870\uac74\uc774 \ucc38\uc778 \ub3d9\uc548 \ubc18\ubcf5\ud569\ub2c8\ub2e4.<\/p>\n
    var n = 1\nwhile n < 100 {\n    n *= 2\n}\nprint(n)  \/\/ 128\n<\/code><\/pre>\n
    repeat-while<\/code>\uc740 \ubcf8\ubb38\uc744 \ucd5c\uc18c \ud55c \ubc88 \uc2e4\ud589\ud558\uace0 \uc870\uac74\uc744 \ud655\uc778\ud569\ub2c8\ub2e4. Python\uc758 while True: ... if ...: break<\/code> \ud328\ud134\uc774\ub098 C\uc758 do-while<\/code>\uc5d0 \ud574\ub2f9\ud569\ub2c8\ub2e4.<\/p>\n
    var input = 0\nrepeat {\n    input += 1\n} while input < 3\nprint(input)  \/\/ 3\n<\/code><\/pre>\n
    \n
    guard \u2014 \uc870\uae30 \ud0c8\ucd9c \ud328\ud134<\/h2>\n
    guard<\/code>\ub294 Swift\uc5d0\uc11c\ub9cc \ubcfc \uc218 \uc788\ub294 \ud0a4\uc6cc\ub4dc\uc785\ub2c8\ub2e4. if<\/code>\uc758 \ubc18\ub300 \ubc29\ud5a5\uc73c\ub85c \ub3d9\uc791\ud55c\ub2e4\uace0 \uc0dd\uac01\ud558\uba74 \ub429\ub2c8\ub2e4.<\/p>\n
    if<\/code>\ub294 “\uc870\uac74\uc774 \ucc38\uc774\uba74 \uc2e4\ud589\ud55c\ub2e4”\uc774\uace0, guard<\/code>\ub294 “\uc870\uac74\uc774 \uac70\uc9d3\uc774\uba74 \uc9c0\uae08 \ube14\ub85d\uc5d0\uc11c \ud0c8\ucd9c\ud55c\ub2e4”\uc785\ub2c8\ub2e4.<\/p>\n
    func greet(name: String?) {\n    guard let name = name else {\n        print(\"\uc774\ub984\uc774 \uc5c6\uc2b5\ub2c8\ub2e4\")\n        return  \/\/ \ubc18\ub4dc\uc2dc \ud0c8\ucd9c\ud574\uc57c \ud568\n    }\n    \/\/ \uc5ec\uae30\uc11c\ubd80\ud130 name\uc740 String (\uc635\uc154\ub110 \uc544\ub2d8)\n    print(\"\uc548\ub155\ud558\uc138\uc694, \\(name)!\")\n}\n\ngreet(name: \"\ucca0\uc218\")   \/\/ \uc548\ub155\ud558\uc138\uc694, \ucca0\uc218!\ngreet(name: nil)      \/\/ \uc774\ub984\uc774 \uc5c6\uc2b5\ub2c8\ub2e4\n<\/code><\/pre>\n
    guard<\/code>\uac00 \uc65c \uc874\uc7ac\ud558\ub294\uc9c0\ub294 if let<\/code>\uacfc \ube44\uad50\ud558\uba74 \ubd84\uba85\ud574\uc9d1\ub2c8\ub2e4.<\/p>\n
    \/\/ if let \ubc29\uc2dd \u2014 \uc720\ud6a8\ud55c \uacbd\uc6b0\uac00 \uc911\ucca9 \uc548\uc73c\ub85c \ub4e4\uc5b4\uac10\nfunc process(value: String?) {\n    if let v = value {\n        if v.count > 0 {\n            if let n = Int(v) {\n                print(\"\uc22b\uc790: \\(n)\")\n            }\n        }\n    }\n}\n\n\/\/ guard \ubc29\uc2dd \u2014 \uc2e4\ud328 \ucf00\uc774\uc2a4\ub97c \uba3c\uc800 \ucc98\ub9ac\ud558\uace0, \uc815\uc0c1 \ud750\ub984\uc740 \ub4e4\uc5ec\uc4f0\uae30 \uc5c6\uc774 \uc774\uc5b4\uc9d0\nfunc process(value: String?) {\n    guard let v = value else { return }\n    guard v.count > 0 else { return }\n    guard let n = Int(v) else { return }\n\n    print(\"\uc22b\uc790: \\(n)\")\n}\n<\/code><\/pre>\n
    \ub450 \ubc88\uc9f8 \ubc29\uc2dd\uc774 \ud6e8\uc52c \uc77d\uae30 \uc27d\uc2b5\ub2c8\ub2e4. “\uc774 \uc870\uac74\uc744 \ub9cc\uc871\ud558\uc9c0 \uc54a\uc73c\uba74 \uc5ec\uae30\uc11c \ub05d\ub0b8\ub2e4”\ub294 \uc608\uc678 \ucf00\uc774\uc2a4\ub97c \ud568\uc218 \uc55e\ucabd\uc5d0\uc11c \uc815\ub9ac\ud558\uace0, \uc815\uc0c1 \uacbd\ub85c\ub294 \ub4e4\uc5ec\uc4f0\uae30 \uc5c6\uc774 \uc120\ud615\uc73c\ub85c \uc774\uc5b4\uc9d1\ub2c8\ub2e4. \uc774\uac83\uc744 \uc870\uae30 \ud0c8\ucd9c(early return)<\/strong> \ud328\ud134\uc774\ub77c\uace0 \ud569\ub2c8\ub2e4.<\/p>\n
    guard<\/code>\ub294 \ubc18\ub4dc\uc2dc return<\/code>, throw<\/code>, break<\/code>, continue<\/code> \uc911 \ud558\ub098\ub85c \ud604\uc7ac \uc2a4\ucf54\ud504\ub97c \ud0c8\ucd9c\ud574\uc57c \ud569\ub2c8\ub2e4. \ud0c8\ucd9c \ucf54\ub4dc\uac00 \uc5c6\uc73c\uba74 \ucef4\ud30c\uc77c \uc624\ub958\uac00 \ub0a9\ub2c8\ub2e4.<\/p>\n
    \n
    break\uc640 continue<\/h2>\n
    \/\/ break: \ubc18\ubcf5\ubb38 \uc989\uc2dc \uc885\ub8cc\nfor i in 1...10 {\n    if i == 5 { break }\n    print(i)  \/\/ 1, 2, 3, 4\n}\n\n\/\/ continue: \ud604\uc7ac \uc21c\ud68c \uac74\ub108\ub6f0\uae30\nfor i in 1...10 {\n    if i % 2 == 0 { continue }\n    print(i)  \/\/ 1, 3, 5, 7, 9\n}\n<\/code><\/pre>\n
    \uc911\ucca9 \ubc18\ubcf5\ubb38\uc5d0\uc11c \ubc14\uae65 \ubc18\ubcf5\ubb38\uc744 \uc81c\uc5b4\ud560 \ub54c\ub294 \ub808\uc774\ube14\uc744 \uc501\ub2c8\ub2e4.<\/p>\n
    outer: for i in 1...3 {\n    for j in 1...3 {\n        if j == 2 { continue outer }  \/\/ \uc548\ucabd \ubc18\ubcf5 \uac74\ub108\ub6f0\uace0 \ubc14\uae65 \ub2e4\uc74c \uc21c\ud68c\ub85c\n        print(\"\\(i)-\\(j)\")\n    }\n}\n\/\/ 1-1, 2-1, 3-1\n<\/code><\/pre>\n
    \n
    \ub2e4\ub978 \uc5b8\uc5b4\uc640 \ube44\uad50<\/h2>\n\n\n\n\n\n\n\n\n\n
    <\/th>\nPython<\/th>\nJavaScript \/ C<\/th>\nSwift<\/th>\n<\/tr>\n<\/thead>\n
    if \uc870\uac74 \uad04\ud638<\/td>\n\ubd88\ud544\uc694<\/td>\n\ud544\uc218<\/td>\n\ubd88\ud544\uc694 (\uad00\ub840)<\/td>\n<\/tr>\n
    switch fallthrough<\/td>\n\uc5c6\uc74c (match)<\/td>\n\uae30\ubcf8 \ub3d9\uc791<\/td>\n\uc5c6\uc74c (\uba85\uc2dc \uc2dc\ub9cc)<\/td>\n<\/tr>\n
    switch \ub9dd\ub77c\uc131<\/td>\n–<\/td>\n\ubd88\ud544\uc694<\/td>\n\ubaa8\ub4e0 \uacbd\uc6b0 \ucc98\ub9ac \ud544\uc218<\/td>\n<\/tr>\n
    do-while<\/td>\n\uc5c6\uc74c<\/td>\n\uc788\uc74c<\/td>\nrepeat-while<\/code><\/td>\n<\/tr>\n
    \uc870\uae30 \ud0c8\ucd9c \ud0a4\uc6cc\ub4dc<\/td>\n\uc5c6\uc74c<\/td>\n\uc5c6\uc74c<\/td>\nguard<\/code><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
    \n
    \ud575\uc2ec \uc694\uc57d<\/h2>\n