The title sounds pretty strange, but I will explain what it means.<\/p>\n\n\n\n
While playing with Swift I’ve faced weird behaviour, a feature in fact, which isn’t covered in documentation (at least I didn’t find any references!).<\/p>\n\n\n\n
UPD:<\/strong> shame on me, how could I miss this?<\/p>\n\n\n\n Global constants and variables are always computed lazily, in a similar manner to Lazy Stored Properties. Unlike lazy stored properties, global constants and variables do not need to be marked with the @lazy attribute.<\/strong><\/p>\n\n\n\n Global variables are functions and their actual values instantiate on demand<\/strong><\/p>\n\n\n\n I wanted to perform some function from different translation unit without explicit calling, and decided to try old C++ trick with global variable:<\/p>\n\n\n\n After compiling and running this program you’ll see “hello, world!” in the output, so I’ve tried the same trick with swift:<\/p>\n\n\n\n But had no luck… This program does nothing in swift.<\/p>\n\n\n\n At the first glance, it looks like compiler optimisation, but what if we call this variable from debugger?<\/p>\n\n\n\n It works. Weird. But it works!<\/p>\n\n\n\n Ok, so let’s access to this variable from The problem<\/h2>\n\n\n\n
#include <iostream>\n\nint globalFunc() \n{\n std::cout << \"hello, world!\\n\";\n return 42;\n}\n\nint globalVar = globalFunc();<\/pre>\n\n\n\nint main(int argc, const char * argv[])\n{\n return 0;\n}<\/pre>\n\n\n\nimport Foundation\n\nfunc globalFunc() -> Int \n{\n println(\"hello, world!\")\n return 42\n}\n\nvar globalVar = globalFunc()<\/pre>\n\n\n\n\/\/ currently, this file is empty<\/pre>\n\n\n\n
Explanation<\/h2>\n\n\n\n
(lldb) po globalVar\nhello, world!\n42\n\n(lldb)<\/pre>\n\n\n\n
main.swift<\/code>:<\/p>\n\n\n\nvar localOne = globalVar<\/pre>\n\n\n\n