global-variables

问题 I tried to use acast from reshape2 within a self written function, but had the problem that acast did not find the data I send to it. Here is my data: library("reshape2") x <- data.frame(1:3, rnorm(3), rnorm(3), rnorm(3)) colnames(x) <- c("id", "var1", "var2", "var3") y <-melt(x, id = "id", measure = c("var1", "var2", "var3")) y then looks like this: id variable value 1 1 var1 0.1560812 2 2 var1 1.0343844 3 3 var1 -1.4157728 4 1 var2 0.8808935 5 2 var2 0.1719239 6 3 var2 0.6723758 7 1 var3 -0

问题 So I can read from a global variable def f() : print x And I can also assign it def g() global x x = 3 When people say "global variables are bad", do they mean that both reading and assigning are bad, or just assigning is bad? (my impression is that reading is not dangerous) 回答1: The problem is not so much "global == bad" so much as "Global mutable state makes it hard to reason about program flow" To illustrate, imagine this function: def frob(): if my_global: wibble() else: wobble() That is,

问题 So I was reading Programing in Lua 2nd Ed and I came across this paragraph here: It is good programming style to use local variables whenever possible. Local variables help you avoid cluttering the global environment with unnecessary names. Moreover, the access to local variables is faster than to global ones . Could anyone explain why this is? And is this "feature" only in Lua, or is it in other languages aswell? (e.g. C, C++, Java) 回答1: The difference in running time is due to the

问题 What would be the most appropriate way of sharing the database connection in the below snippet ( the db variable) with my routers/controllers without turning the db variable into a global? var mongo = require('mongoskin'), db = mongo.db(config.db.adress); app.use(function(req, res, next) { db.open(function(err, data) { (err) ? res.send('Internal server error', 500) : next(); }); }); // Setting up controllers here app.post('/users', require('./controllers/users').create); Coming from a PHP

问题 How can I get the current role name in an ansible task yaml file? I would like to do something like this --- # role/some-role-name/tasks/main.yml - name: Create a directory which is called like the current role name action: file path=/tmp/"{{ role_name }}" mode=0755 state=directory The result of this task should be a directory /tmp/some-role-name on the server 回答1: As of Ansible 2.2 : {{role_name}} As of Ansible 2.1 : {{role_path|basename}} Older versions: There is no way to do this in the

问题 How can I get the current role name in an ansible task yaml file? I would like to do something like this --- # role/some-role-name/tasks/main.yml - name: Create a directory which is called like the current role name action: file path=/tmp/"{{ role_name }}" mode=0755 state=directory The result of this task should be a directory /tmp/some-role-name on the server 回答1: As of Ansible 2.2 : {{role_name}} As of Ansible 2.1 : {{role_path|basename}} Older versions: There is no way to do this in the

问题 I'm a very newbie on CodeIgniter, and while I go on I run into problems that, in the procedural coding, were easy to fix The current issue is: I have this controller class Basic extends Controller { function index(){ $data['title'] = 'Page Title'; $data['robots'] = 'noindex,nofollow'; $data['css'] = $this->config->item('css'); $data['my_data'] = 'Some chunk of text'; $this->load->view('basic_view', $data); } function form(){ $data['title'] = 'Page Title'; $data['robots'] = 'noindex,nofollow';

问题 I am trying to implement a movement system where the player move's towards the click position. But I have been running into some problems with the arguments of the movement method. The movement method currently needs to take all the variables as arguments: This code works: def move(self,event,mouse_pos, screen, background): if event.type == MOUSEBUTTONDOWN: if mouse_pos[1] > self.pos[1]: screen.blit(background, self.pos, self.pos) #erases players by bliting bg self.speed = 1 self.move_south()

问题 I need to stock some datas in my application. I know that i can do it like this: class: public class MyApplication extends Application { private String someVariable; public String getSomeVariable() { return someVariable; } public void setSomeVariable(String someVariable) { this.someVariable = someVariable; } } Implementation: MyApp appState = ((MyApp)getApplicationContext()); String state = appState.getSomeVariable(); This is working if i'm in an activity. But if i'm in a class not extended

问题 This code: $t = 100; $str = preg_replace_callback("/(Name[A-Z]+[0-9]*)/", create_function( '$matches', 'return $matches[1] + $t;' ), $func); How to make $t visible from create_function() in preg_replace() function? 回答1: An anonymous function would work, while making use of the use syntax: $t = 100; $str = preg_replace_callback("/(Name[A-Z]+[0-9]*)/", function($matches) use($t) // $t will now be visible inside of the function { return $matches[1] + $t; }, $func); 回答2: You can't make the