\ud83d\udc49\ud83c\udffb \ub2e4\uc74c\ucf54\ub4dc\ucc98\ub7fc \ub78c\ub2e4\ud568\uc218\ub780 \uc774\ub984\uc5c6\ub294 \uc775\uba85\ud568\uc218\ub97c \uc758\ubbf8\ud569\ub2c8\ub2e4.
As shown in the following code, a lambda function refers to an unnamed anonymous function.<\/p>\n\n\n\n
[&](const std::string& req) -> std::string {\n return router(req);\n }<\/code><\/pre>\n\n\n\n\ud83d\udc49\ud83c\udffb \uc704\uc640 \uac19\uc740 \ub78c\ub2e4\ud568\uc218\ub97c \ud30c\ub77c\uba54\ud130\ub85c \ub2e4\ub978 \ud568\uc218\uc5d0 \uc804\ub2ec \ud560 \uc218 \uc788\uc2b5\ub2c8\ub2e4. \uc774\uac83\uc744 \ucf5c\ubc31\ud568\uc218\ub77c\uace0 \ud569\ub2c8\ub2e4.
You can pass a lambda function like the one above as a parameter to another function. This is called a callback function.<\/p>\n\n\n\n
my_sv.set_handler([&](const std::string& req) -> std::string {\n return router(req);\n });<\/code><\/pre>\n\n\n\n\ud83d\udc49\ud83c\udffb \ub78c\ub2e4\ud568\uc218\uc5d0\uc11c [&] \uc774\uac83\uc744 \ucea1\ucdb0\ub9ac\uc2a4\ud2b8\ub77c\uace0 \ud569\ub2c8\ub2e4.
In lambda functions, [&] is called a capture list.<\/p>\n\n\n\n
\ud83d\udc49\ud83c\udffb \ucea1\ucdb0 \ub9ac\uc2a4\ud2b8\uc5d0\ub294 \ub2e4\uc74c\uacfc \uac19\uc740 \uc885\ub958\uac00 \uc788\uc2b5\ub2c8\ub2e4.
The capture list includes the following types.<\/p>\n\n\n\n\uad6c\ubb38\/Syntax<\/th> \uc758\ubbf8\/Meaning<\/strong><\/th>\ud2b9\uc9d5\/Features<\/th> \uc0ac\uc6a9 \uc608\uc2dc\/Usage Examples<\/th><\/tr><\/thead> []<\/code><\/td>\uc544\ubb34\uac83\ub3c4 \ucea1\ucc98\ud558\uc9c0 \uc54a\uc74c \/ Capturing nothing<\/td> \ucea1\ucc98\ud560 \uc678\ubd80 \ubcc0\uc218\uac00 \uc5c6\uc744 \ub54c \uc0ac\uc6a9 \/
Used when there are no external variables to capture.<\/td> [](){ ... }<\/code><\/td><\/tr>[var1, var2]<\/code><\/td>\ud2b9\uc815 \ubcc0\uc218\ub9cc \uba85\uc2dc\uc801 \ucea1\ucc98 \/ Explicitly capture only specific variables<\/td> \ud544\uc694\ud55c \ubcc0\uc218\ub9cc \uace8\ub77c \uac00\uc838\uc62c \ub54c \/
When selecting and retrieving only the necessary variables<\/td> [i, j]()<\/code><\/td><\/tr>[=]<\/code><\/td>\ubaa8\ub4e0 \uc678\ubd80 \ubcc0\uc218\ub97c \uac12\uc73c\ub85c \ubcf5\uc0ac \/ Copy all external variables by value<\/td> \ud604\uc7ac \ubc94\uc704\uc758 \ubaa8\ub4e0 \ubcc0\uc218\ub97c \uac12\uc73c\ub85c \ubcf5\uc0ac\ud558\uc5ec \uc0ac\uc6a9\ud569\ub2c8\ub2e4. \/
Copy all variables in the current range by value and use them.<\/td> [=]()<\/code><\/td><\/tr>[&]<\/code><\/td>\ubaa8\ub4e0 \uc678\ubd80 \ubcc0\uc218\ub97c \ucc38\uc870\ub85c \uc0ac\uc6a9 \/ Use all external variables by reference<\/td> \ud604\uc7ac \ubc94\uc704\uc758 \ubaa8\ub4e0 \ubcc0\uc218\ub97c \ucc38\uc870\ub85c \uc0ac\uc6a9\ud569\ub2c8\ub2e4. \/
Uses all variables in the current range as references.<\/td> [&]()<\/code><\/td><\/tr>[&var]<\/code><\/td>\ud2b9\uc815 \ubcc0\uc218\ub97c \ucc38\uc870\ub85c \ucea1\ucc98 \/ Capturing a specific variable by reference<\/td> \uc6d0\ud558\ub294 \ubcc0\uc218\ub9cc \uc9c0\uc815\ud558\uc5ec \ucc38\uc870\ub85c \uc0ac\uc6a9\ud560 \ub54c \/
When using references by specifying only the desired variables<\/td> [&i]()<\/code><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n\ud83d\udc49\ud83c\udffb \ucea1\ucdb0 \ub9ac\uc2a4\ud2b8\uc758 \ubc94\uc704\ub294 main()\ud568\uc218 \uc804\uccb4 \ubc94\uc704 \uc785\ub2c8\ub2e4.
The range of the capture list is the entire range of the main() function.<\/p>\n\n\n\n
\ud83d\udc49\ud83c\udffb -> std::string \uc774 \ubd80\ubd84\uc740 \ubc18\ud658\ub418\ub294 \uac12\uc758 \ud0c0\uc785\uc785\ub2c8\ub2e4.
-> std::string This part is the type of the returned value.<\/p>\n\n\n\n
\ud83d\udc49\ud83c\udffb\ucf54\ub4dc \/ Code<\/p>\n\n\n\n
\u2714\ufe0f \uc544\ub798\ub294 \ub78c\ub2e4\ud568\uc218\uc640 \ucf5c\ubc31\ud568\uc218 \ud328\ud134\uc744 \uc0ac\uc6a9\ud574\uc11c \uc790\uc8fc \uad6c\ud604\ub418\ub294 \ucf54\ub4dc \ud328\ud134\uc911\uc758 \ud558\ub098\uc785\ub2c8\ub2e4.
Below is one of the code patterns frequently implemented using lambda functions and callback function patterns.<\/p>\n\n\n\n
\u2714\ufe0f main.cpp<\/p>\n\n\n\n
#include <iostream>\n#include <string>\n#include <functional>\n#include <vector>\n\nclass Server {\npublic:\n \/\/ \ub85c\uc9c1\uc744 \ub2f4\uc744 \ud568\uc218 \uc800\uc7a5\uc18c (\ub78c\ub2e4\ub97c \ub2f4\ub294 \uadf8\ub987)\n \/\/ Function repository to hold logic (container for Lambda)\n std::function<std::string(const std::string&)> logic_handler;\n\n \/\/ \ud578\ub4e4\ub7ec \uc124\uc815 \uba54\uc11c\ub4dc(logic_handler\uc5d0\uc11c \uc678\ubd80 \ud568\uc218 handler \uc5f0\uacb0)\n \/\/ handler\ud568\uc218\uc5d0\ub294 \uc775\uba85\ud568\uc218\ub85c\uc368 \ubb38\uc790\uc5f4 \uc785\ub825\ubc1b\uace0 router\ud568\uc218 \ub9ac\ud134\n \/\/ Handler configuration method (connecting the external function handler in logic_handler)\n \/\/ The handler function receives a string as an anonymous function and returns the router function\n\n void set_handler(std::function<std::string(const std::string&)> handler) {\n logic_handler = handler;\n }\n\n \/\/ \ud074\ub77c\uc774\uc5b8\ud2b8 \uc694\uccad\uc744 \ucc98\ub9ac\ud558\ub294 \uac00\uc0c1 \uba54\uc11c\ub4dc\n \/\/ Virtual method that handles client requests\n void receive_request(const std::string& message) {\n std::cout << \"[Server] \uc694\uccad \ubc1b\uc74c \/ Requested: \" << message << std::endl;\n\n if (logic_handler) {\n\n \/\/ \uc678\ubd80\uc5d0\uc11c \uc815\uc758\ud55c \ub78c\ub2e4 \ud568\uc218\uac00 \uc5ec\uae30\uc11c \uc2e4\ud589\ub429\ub2c8\ub2e4!\n \/\/ login_handler\ub294 router \ud568\uc218\uc758 \uac12\uc744 \ub9ac\ud134\n \/\/ The externally defined Lambda function is executed here!\n \/\/ login_handler returns the value of the router function\n\n std::string response = logic_handler(message);\n std::cout << \"[Server] \uc751\ub2f5 \ubcf4\ub0c4 \/ Reply sent: \" << response << \"\\n\" << std::endl;\n } else {\n std::cout << \"[Server] \ucc98\ub9ac\ud560 \ud578\ub4e4\ub7ec\uac00 \uc5c6\uc2b5\ub2c8\ub2e4\/There is no handler to process..\\n\" << std::endl;\n }\n }\n};\n\nstd::string router(const std::string& msg) {\n if (msg == \"aloy\") return \"horizon\";\n if (msg == \"silverhand\") return \"cyberpunk\";\n return \"unknown command\";\n}\n\nint main() {\n Server my_sv;\n\n \/\/ \ub78c\ub2e4 \ud568\uc218\ub97c \uc0ac\uc6a9\ud558\uc5ec \ub85c\uc9c1 \uc5f0\uacb0 \/ Connecting logic using lambda functions\n my_sv.set_handler([&](const std::string& req) -> std::string {\n return router(req);\n });\n\n \/\/ \uc694\uccad \/ requests\n my_sv.receive_request(\"aloy\");\n my_sv.receive_request(\"silverhand\");\n my_sv.receive_request(\"npc\");\n\n return 0;\n}\n<\/code><\/pre>\n\n\n\n\u2714\ufe0f \ucef4\ud30c\uc77c \/ Compiling<\/p>\n\n\n\n
g++ main.cpp -o main -std=c++17<\/code><\/pre>\n\n\n\n\u2714\ufe0f \uc2e4\ud589 \/ Run<\/p>\n\n\n\n
.\/main<\/code><\/pre>\n\n\n\n\u2714\ufe0f \uacb0\uacfc \/ Resutl<\/p>\n\n\n\n
rambda_function % .\/main\n[Server] \uc694\uccad \ubc1b\uc74c: aloy\n[Server] \uc751\ub2f5 \ubcf4\ub0c4\/Reply sent: horizon\n\n[Server] \uc694\uccad \ubc1b\uc74c: silverhand\n[Server] \uc751\ub2f5 \ubcf4\ub0c4\/Reply sent: cyberpunk\n\n[Server] \uc694\uccad \ubc1b\uc74c: npc\n[Server] \uc751\ub2f5 \ubcf4\ub0c4\/Reply sent: unknown command\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"\ud83d\udc49\ud83c\udffb \ub2e4\uc74c\ucf54\ub4dc\ucc98\ub7fc \ub78c\ub2e4\ud568\uc218\ub780 \uc774\ub984\uc5c6\ub294 \uc775\uba85\ud568\uc218\ub97c \uc758\ubbf8\ud569\ub2c8\ub2e4.As shown in the following code, a lambda function refers to an unnamed anonymous function. \ud83d\udc49\ud83c\udffb \uc704\uc640 \uac19\uc740 \ub78c\ub2e4\ud568\uc218\ub97c \ud30c\ub77c\uba54\ud130\ub85c \ub2e4\ub978 \ud568\uc218\uc5d0 \uc804\ub2ec \ud560 \uc218 \uc788\uc2b5\ub2c8\ub2e4. \uc774\uac83\uc744 \ucf5c\ubc31\ud568\uc218\ub77c\uace0 \ud569\ub2c8\ub2e4.You can pass a lambda function like the one above as a parameter to another function. This is called a callback function. […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23,1],"tags":[],"class_list":["post-5444","post","type-post","status-publish","format-standard","hentry","category-cpp","category-uncategorized","missing-thumbnail"],"_links":{"self":[{"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/5444","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/comments?post=5444"}],"version-history":[{"count":3,"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/5444\/revisions"}],"predecessor-version":[{"id":5447,"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/5444\/revisions\/5447"}],"wp:attachment":[{"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/media?parent=5444"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/categories?post=5444"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/wp-json\/wp\/v2\/tags?post=5444"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}