global-variables

问题 I'm new to iPhone development so want to ask, what is the best way to keep global variables and constants which can be accessed by many classes? Shall I keep them in app delegate or there is a better way which I don't know? Thanks 回答1: Keeping them in the app delegate is one solution, though it's not particularly elegant to shove everything into a class whose purpose is really to respond to events related to the application. For constants, you can simply create header files and use #define or

问题 In C, each function has an activation record which is allocated on a stack frame. Local variables are allocated in their own function's activation record. So, what is the case with global variables? Where are they allocated? For example #include <stdio.h> int a; void v() {a= 2; int b; b++; } main() { int f; printf("\n%d",a); v(); } -----Activation record---- ------------------- ------------------- activation record for main ------------------- int f ------------------- -------------------

问题 In C, each function has an activation record which is allocated on a stack frame. Local variables are allocated in their own function's activation record. So, what is the case with global variables? Where are they allocated? For example #include <stdio.h> int a; void v() {a= 2; int b; b++; } main() { int f; printf("\n%d",a); v(); } -----Activation record---- ------------------- ------------------- activation record for main ------------------- int f ------------------- -------------------

问题 In python, is it better that using the singleton pattern instead of using global variable? class Singleton(type): def __call__(self, *args, **kwargs): if 'instance' not in self.__dict__: self.instance = super(Singleton, self).__call__(*args, **kwargs) return self.instance or just make a global variable: SINGLETON_VARIABLE = None def getSingleton(): if SINGLETON is None: SINGLETON_VARIABLE = SOME_ININ_CLASS() return SINGLETON_VARIABLE Is it necessary to complicate the life to make a singleton

问题 I'm trying to host a PHP web site that was given to me. I see this warning: Warning: Unknown: Your script possibly relies on a session side-effect which existed until PHP 4.2.3. Please be advised that the session extension does not consider global variables as a source of data, unless register_globals is enabled. You can disable this functionality and this warning by setting session.bug_compat_42 or session.bug_compat_warn to off, respectively. in Unknown on line 0 What does this mean? How

问题 I want to define a few variables in my main python script and use them in a function which is defined in a separate module. Here is an example code. Lets say the main script is named main.py and the module is called mod.py. Mod.py def fun(): print a main.py from mod import * global a a=3 fun() Now, this code gives me an error NameError: global name 'a' is not defined Can anyone please explain why the error is generated (i mean, a variable defined as global should be available to all functions

问题 Global Reference in JNI is said to be a reference that has to be manually freed by the programmer. It has nothing to do with the c context. so a code like : { jclass clsStr = (*env)->NewGlobalRef(env,cls); } return clsStr; will give an error saying that clsStr is undefined / undeclared . I understand this. But what i don't understand is the use of these type of references. What is global about clsStr in the above code ? How this variable can be useful in future or after the call returns ? I

问题 How can I export the global environment for the beginning of each parallel simulation in foreach? The following code is part of a function that is called to run the simulations. num.cores <- detectCores()-1 cluztrr <- makeCluster(num.cores) registerDoParallel(cl = cluztrr) sim.result.list <- foreach(r = 1:simulations, .combine = list, .multicombine = TRUE, ) %dopar% { #...tons of calculations using many variables... list(vals1, vals2, vals3) } stopCluster(cluztrr) Is it necessary to use

问题 What are the pros and cons of storing data in: Hidden input fields Cookies/local storage Server side sessions 回答1: Those three are not mutually exclusive things. hidden input A hidden input is just HTML sent to the client. It does not appear on the page to the end-user, but it is entirely accessible to the client. Meaning that the user can see it (just as they can see any HTTP response from your server) by using the View Source feature in their browser. cookie A cookie is just another HTTP

问题 I have a module in file global.jl which defines a global multidimensional array named "data": module Global export data # GLOBAL DATA ARRAY data = zeros(Int32, 20, 12, 31, 24, 60, 5); end I have a main.jl which uses this global variable: include("global.jl") using .Global println(data[14,1,15,18,0,1]) And I get the following error: $ time /usr/local/julia-1.2.0/bin/julia main.jl ERROR: LoadError: BoundsError: attempt to access 20Ã12Ã31Ã24Ã60Ã5 Array{Int32,6} at index [14, 1, 15, 18, 0, 1]