global

问题 I tried the following struct mbuf { cacheline: *mut [u64], // great amount of rows follows below // .......... } static mut arr: [mbuf; 32]; // Q1 my main aim // something as before but using Vec; // Q2 also main aim fn main() { // let static mut arr: [mbuf; 32]; // Q3 also doesn't work // static mut arr: [mbuf; 32]; // Q3 also doesn't work } and got error src/main.rs:74:29: 74:30 error: expected one of `+` or `=`, found `;` src/main.rs:74 static mut arr: [mbuf; 32]; ^ Q1,Q2,Q3 - Is it

问题 f=1 def skip(i): global f +=i return What's wrong? I don't know >>> f 1 >>> skip(3) Traceback (most recent call last): File "<pyshell#10>", line 1, in <module> skip(3) File "C:/Users/PC/Desktop/game.py", line 4, in skip f +=i UnboundLocalError: local variable 'f' referenced before assignment 回答1: The global statement goes on a separate line: def skip(i): global f f += i The return is redundant here; I've left it off. The global statement 'marks' names in a function as global; it is a distinct

问题 After reading through mozilla docs I found this: In the global execution context (outside of any function), this refers to the global object, whether in strict mode or not. After playing with scopes for a little I found that in node.js REPL... > this === global true but when I create a script with the same line... $ cat > script.js console.log(this === global) $ node script.js false Is there a reason for this? Or is it a bug? 回答1: Node's REPL is global. Code from a file is in a "module",

问题 in this react example from https://reactjs.org/docs/hooks-custom.html, a custom hook is used in 2 different components to fetch online status of a user... function useFriendStatus(friendID) { const [isOnline, setIsOnline] = useState(null); useEffect(() => { function handleStatusChange(status) { setIsOnline(status.isOnline); } ChatAPI.subscribeToFriendStatus(friendID, handleStatusChange); return () => { ChatAPI.unsubscribeFromFriendStatus(friendID, handleStatusChange); }; }); return isOnline;

问题 Is there a way to access one instance of a class inside functions in PHP? Like this: include("class.php"); $bla=new Classname(); function aaa(){ $bla->DoSomething(); //Doesn't work. } $bla->DoSomething(); //Works. 回答1: If I interpret your question correctly, then the proper way to do this is create a singleton class. class Singleton { private static $instance; private function __construct() {} private function __clone() {} public static function getInstance() { if (!Singleton::$instance

问题 Is there a way to access one instance of a class inside functions in PHP? Like this: include("class.php"); $bla=new Classname(); function aaa(){ $bla->DoSomething(); //Doesn't work. } $bla->DoSomething(); //Works. 回答1: If I interpret your question correctly, then the proper way to do this is create a singleton class. class Singleton { private static $instance; private function __construct() {} private function __clone() {} public static function getInstance() { if (!Singleton::$instance

问题 From some sbt document(e.g. scopes), I see: {.}/*:name means name in entire build (use name in ThisBuild to define it) */*:name means name in global project (use name in Global to define it) (PS: I ignored the config part *: ) But, I still don't know what is the difference between them, they seem exactly the same to me. Is there any thing I can do with one rather than another one? 回答1: Whatever version you specified in ThisBuild will be applied to all projects in your build, overriding

问题 I have a shared resource with high initialisation cost and thus I want to access it across the system (it's used for some instrumentation basically, so has to be light weight). So I created a module managing the setup and access to it. It does a lazy initialise of the resource and stores it in a module global variable. I then use functions of this module across the system to operate on the resource. - Now I am wondering whether (or how often) I will have to reinitialise the resource? - I know

问题 This question already has answers here : What is the difference between Const and Static in C#? (5 answers) Closed 4 years ago . what is the difference between "static" and "const" when it comes to declare global variables; namespace General { public static class Globals { public const double GMinimum = 1e-1; public const double GMaximum = 1e+1; } } which one is better (considering that these variables wont be changing ever) namespace General { public static class Globals { public static

问题 What is the reason of having globals() function in Python? It only returns dictionary of global variables, which are already global, so they can be used anywhere... I'm asking only out of curiosity, trying to learn python. def F(): global x x = 1 def G(): print(globals()["x"]) #will return value of global 'x', which is 1 def H(): print(x) #will also return value of global 'x', which, also, is 1 F() G() H() I can't really see the point here? Only time I would need it, was if I had local and