global

问题 Okay, I'm not sure I'm understanding this concept properly (I'm learning PHP). If I understand correctly: Global variables can be referenced anywhere in the same document, or in documents linked with "include." Local variables can only be referenced in the function where they are. Okay, if I understand that correctly (which is half of the reason I'm posting, to make sure I have that right) is there really a need for local variables? I mean, if each user defined their own variables and they

问题 What is the difference between global variable and shared instance in Swift? what are their respective field of use? Could anyone clarify their concept based upon Swift. 回答1: A global variable is a variable that is declared at the top level in a file. So if we had a class called Bar , you could store a reference to an instance of Bar in a global variable like this: var bar = Bar() You would then be able to access the instance from anywhere, like this: bar bar.foo() A shared instance, or

问题 I have a question and i suppose this is trivial for most around here. However, here goes -- I have an application that connects to a database to read specific information. Now this read happens across many classes in the application on a per request basis. So i wanted to restrict the number of connections to the database to 1 per request . So this is what i did. Assuming that i had a database access class, DBAccess that fetches 2 strings, a & b. I wrote a class Global that goes as follows --

问题 I have a question and i suppose this is trivial for most around here. However, here goes -- I have an application that connects to a database to read specific information. Now this read happens across many classes in the application on a per request basis. So i wanted to restrict the number of connections to the database to 1 per request . So this is what i did. Assuming that i had a database access class, DBAccess that fetches 2 strings, a & b. I wrote a class Global that goes as follows --

问题 What is the concept when we define a global array with no dimension This shows output as 16. #include <stdio.h> #include <stdlib.h> int arr[]; int main(int argc, char *argv[]) { arr[1] = 16; printf("%d\n",arr[1]); system("PAUSE"); return 0; } And even sizeof(arr) doesn't work. Why? 回答1: int arr[]; is a tentative definition there. Clause 6.9.2, paragraph 2 says: A declaration of an identifier for an object that has file scope without an initializer, and without a storage-class specifier or

问题 I was going through the Difference between var and let documentation example and was testing that when an undeclared variable is invoked, the global scope automatically provides a declaration for it (that's why the following snippet does not throw an error in any of the variables): x = 3; console.log(x); (function() { y=x+39; })() console.log(y); However, when one variable is declared with let after the assignment in the same global scope: x=3; let x = 42; console.log(x); One of the following

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 4 years ago . I was reading a question about the Python global statement ( "Python scope" ) and I was remembering about how often I used this statement when I was a Python beginner (I used global a lot) and how, nowadays, years later, I don't use it at all, ever. I even consider it a bit "un

问题 i encountered a problem when write python threading code, that i wrote some workers threading classes, they all import a global file like sharevar.py, i need a variable like regdevid to keep tracking the register device id, then when one thread change it's value, then other threads can get it fresh, but the result is that: when one thread change it's value, the others still get the default value i defined in sharevar.py file, why? anything wrong with me? # thread a from UserShare import

问题 i encountered a problem when write python threading code, that i wrote some workers threading classes, they all import a global file like sharevar.py, i need a variable like regdevid to keep tracking the register device id, then when one thread change it's value, then other threads can get it fresh, but the result is that: when one thread change it's value, the others still get the default value i defined in sharevar.py file, why? anything wrong with me? # thread a from UserShare import

问题 A part of a small project I am working on involves 'calibrating' the coordinates of the screen of which to take a screen capture of. By the 'screen', I refer to the entire desktop, not my GUI window. The coordinates are calibrated when a QDialog window appears (which I've subclassed). The user is prompted to click several locations on the screen. I need the program to record the locations of all mouse clicks occuring anywhere on the screen - ones that don't natively trigger a QDialog