global-variables

问题 I have few variables which are used system-wide in my rails app. It runs well if I just have one user using the app. If there are more then one user, many unexpected problem pop out. I don't get any error log, and I have many unexpected behaviors. I believe most of those strange response are due to unexpected change of global variable. I would like to know, is the value of global variable in Rails shared between different users? thanks~ 回答1: This seems to be dependant upon your method of

问题 // in ClassA.h static NSString *globalStr = @"HelloWorld"; @interface ClassA ... @end // in ClassB.h #include "ClassA.h" // in ClassB.m ... NSLog(@"The global string: %@", globalStr); ... In C++, "static" should mean the variable or function has a internal linkage. But it is used to share the variable in this case, error will occur without the static keyword. I'm confused, could someone tell me the concept behind? Thanks! 回答1: static means exactly the same thing in Objective-C that in means

问题 I hope this isn't beating a dead horse, but I'd like an opinion about another possible strategy for writing referentially transparent code. (The previous discussion about referential transparency is at Using a Closure instead of a Global Variable). Again, the objective is to eliminate most global variables, but retain their convenience, without injecting bug-prone references or potentially non-functional behavior (ie, referential opaqueness, side-effects, and non-repeatable evaluations) into

问题 I have code as follow: #include <stdio.h> int g_a; int g_b; int g_c; int main() { printf("Hello world\n"); return 0; } And build it with gcc gcc -o global global.c Finally, I use objdump to see address of global variables objdump -t global And see the result: 00004020 g_b 00004024 g_a 00004028 g_c Why are global variables stored in addresses like above? I mean global variables should be stored in order g_a, g_b, g_c 回答1: global variables should be stored in order g_a, g_b, g_c No, the order

问题 I'm having a bit of trouble capturing the value of a global variable in my $.get() callback: Relevant markup <div class="block" id="blog"></div> <div class="block" id="music"></div> <div class="block" id="video"></div> Relevant code $('div.block').each(function() { $this_id = $(this).attr('id'); alert($this_id); // outputs: blog, music, video $.get('test.php', {id: $this_id}, function(data) { alert($this_id); // outputs: blog, blog, blog (WHY?) $('div#' + $this_id).html(data); }); }); I'm

问题 I have a fortran library to which I must pass a function with a very specific format. The library then is doing some operation on my function. The function is written by a user (like me) and the library is given for granted. Unfortunately to compute my function I need some values (some of them could be initialized once and for all in the main) and I would like to avoid the use of common or save . I read I could use a singleton pattern but I am not very expert in template and on top of that

问题 I have a global variable called userValue. When the page loads, this value is finding the selected option and storing that options value. On load it would be storing default or null since the option is disabled. However, onchange (more options populate dynamically per site), I'm trying to store the value of the selected option globally so I can simply keep reusing the varialbe userValue. What I have below works properly when I include: userValue = $('#my_SiteUsers').find(':selected').val();

问题 I have an application that displays a list of photo albums and then, once an album is selected, displays photos in that album. I am using the memory cache/disk cache implementation from one of the google examples (since the photos are loaded from a website). Everything is working fine, but the disk cache initialization takes place every time an album is chosen, and the initialization takes considerable amount of time. I'd like to declare the disk cache "globally" and use it for all albums. I

问题 As of now I create a variable like this in a file that's loaded on all pages: <?php add_action( 'parse_query', 'my_global_vars' ); function my_global_vars() { /* CUSTOM GLOBAL VARIABLES */ $variable_name = get_query_var('category_name'); } ?> And every time I want to use it (in other files), I must do it like this: <?php global $variable_name; if( $variable_name = 'news' ){ // Do something } ?> And when I need to use the variable multiple times in the same file, I add global $variable_name;

问题 When you create a new repl instance in code it automatically has access to anything in global scope. You can modify the repl context to expose some custom variables in local scope so that the repl can access them, but I don't see an easy way to eliminate access to the global scope. I wish I could just give the repl a new blank global scope. Here is an example repl instance: var repl = require('repl'), msg = "Hello world!"; repl.start('> ').context.msg = msg; In that repl I typed out the