global-variables

问题 What i want to do is just display the firstevent from one API. The variable is called “firstevent” and the value should display on the webpage. But firstevent is inside a def, so i change it into a global variable and hope it can be used across different functions. But it shows “NameError: global name 'firstevent' is not defined”. This is what I am doing: define a global variable global firstevent send this variable a random value, it supposed to be events['items'][1]['end'] firstevent = 1

问题 When I write the following program: file 1: #include <stdio.h> int global; void print_global1() { printf("%p\n", &global); } file 2: #include <stdio.h> char global; void print_global2() { printf("%p\n", &global); } file 3: void print_global1(); void print_global2(); int main() { print_global1(); print_global2(); return 0; } output: $ ./a.out 0x804a01c 0x804a01c Here is my question: Why are the linker implementing "int global" and "char global" as the same global variable: How come the

问题 I have a google appengine app where I want to set a global variable for that request only. Can I do this? In request_vars.py # request_vars.py global_vars = threading.local() In another.py # another.py from request_vars import global_vars get_time(): return global_vars.time_start In main.py # main.py import another from request_vars import global_vars global_vars.time_start = datetime.datetime.now() time_start = another.get_time() Questions: Considering multithreading, concurrent requests,

问题 I have this simple c++ code : #include<bits/stdc++.h> using namespace std; vector<string> q; int main() { q.push_back("test1"); q.push_back("test2"); cout<<q.front(); return 0; } When I use gdb to print variable q I get following error: No symbol "q" in current context. I compile my program using g++ like this: g++ -g a.cpp And here is my gdb commands: gdb a.out GNU gdb (GDB) 7.12 Copyright (C) 2016 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org

问题 So I get the 'initializer element not constant' error when compiling the following code: #include <stdlib.h> #include <stdio.h> #include <math.h> float wl = 2.0f; float k = 2.0f * (float) M_PI / wl; int main () { //Do stuff } If I move "float k" inside the main method, there's no errors, but this isn't an option for me, because I NEED float k to be a global variable. Even if I change it to this: const float wl = 2.0f; const float k = 2.0f * (float) M_PI / wl; the error still happens. How do I

问题 So, there are dozens of built-in global properties in the (desktop) browser. For instance: document undefined parseInt JSON location alert setTimout etc. When referring to those properties, should one explicitly note them as global properties by prefixing their name with window. ? So, for instance: var wrap = window.document.getElementById('wrap'); and window.setTimeout(loop, 100); and var x = window.parseInt(input.value, 10); I think there are three answers to this question: Yes, you should

问题 I'm new to fat free framework and i'm a little bit confused about the global variables. $f3->route('GET /@page','display'); function display($f3) { echo 'I cannot object to an object' . $f3->get('PARAMS.page'); }; $f3->run(); Here i'm using GET /@page as a token for the url route. In the function i then use $f3->get('PARAMS.page') to get the value of that variable. Since $f3->get is the method to get a global variable, why do i have to pass the $f3 class to the function. The below code doesn

问题 I'm building an iOS application. Most of the application requires access to a persistent object. This object is instantiated when the app loads via the Application Delegate. The problem I have is that numerous View Controllers that need to access this object. What is the best way and best practice to create global objects that can be access from anywhere in the application? Examples would be appreciated. Many thanks. 回答1: You might want to look at the Singleton pattern. The linked article

问题 Should I use private or fileprivate to declare global variables/consts in Swift 3? e.g. fileprivate let a = 1 fileprivate class SomeClass { fileprivate b = 0 } Or private let a = 1 private class someClass { fileprivate b = 0 } 回答1: It really makes no difference at file level, whether you use private of fileprivate , access control will be the same, for example constants defined this way will be only usable in that file. Same can be said for other modifiers, in certain cases, internal and

问题 x = 1; alert(x); var y = function() { alert(x); var x = 2; alert(x); } y(); The result of the 3 alerts is: 1 , undefined , 2 (Chrome 25) My question is: why the second alert is undefined? Why not 1? Isn't there a global variable x? 回答1: Due to hoisting, this is what gets executed: x = 1; alert(x); var y = function() { var x; // <-- this gets hoisted up from where it was. alert(x); x = 2; alert(x); } y(); At the start of function y() , the local variable x is declared but not initialized. 回答2: