[Declarar Una Variable Global En Visual Basic
Addison Mauldin
However, you'll need to fully-qualify all references to those variables anywhere you want to use them in your code. In this sense, they are not the type of global variables with which you may be familiar from other languages, because they are still associated with some particular class.
If the practice of fully-qualifying your variables horrifies or upsets you for whatever reason, you can always import the class that contains your global variable declarations (here, GlobalVariables) at the top of each code file (or even at the project level, in the project's Properties window). Then, you could simply reference the variables by their name.
Note that this is exactly the same thing that the compiler is doing for you behind-the-scenes when you declare your global variables in a Module, rather than a Class. In VB.NET, which offers modules for backward-compatibility purposes with previous versions of VB, a Module is simply a sealed static class (or, in VB.NET terms, Shared NotInheritable Class). The IDE allows you to call members from modules without fully-qualifying or importing a reference to them. Even if you decide to go this route, it's worth understanding what is happening behind the scenes in an object-oriented language like VB.NET. I think that as a programmer, it's important to understand what's going on and what exactly your tools are doing for you, even if you decide to use them. And for what it's worth, I do not recommend this as a "best practice" because I feel that it tends towards obscurity and clean object-oriented code/design. It's much more likely that a C# programmer will understand your code if it's written as shown above than if you cram it into a module and let the compiler handle everything.
Note that like at least one other answer has alluded to, VB.NET is a fully object-oriented language. That means, among other things, that everything is an object. Even "global" variables have to be defined within an instance of a class because they are objects as well. Any time you feel the need to use global variables in an object-oriented language, that a sign you need to rethink your design. If you're just making the switch to object-oriented programming, it's more than worth your while to stop and learn some of the basic patterns before entrenching yourself any further into writing code.
That type of coding seems to have worked on my VB2008 Express and seems to be all needed at the moment (void of any unknown files being loaded in the background) even though I have found no end to the "Oh btw..." surprise details. And I'm certain a greater degree of standardization would be preferred, but the first task is simply to get something working at all, with or without standards.
A global variable could be accessible in all your forms in your project if you use the keyword public shared if it is in a class. It will also work if you use the keyword "public" if it is under a Module, but it is not the best practice for many reasons.
One of the problems is when you have two threads that call the same global variable at the same time. You will have some surprises. You might have unexpected reactions if you don't know their limitations. Take a look at the post Global Variables in Visual Basic .NET and download the sample project!
small remark: I am using modules in webbased application (asp.net).I need to remember that everything I store in the variables on the module are seen by everyone in the application, read website. Not only in my session.If i try to add up a calculation in my session I need to make an array to filter the numbers for my session and for others.Modules is a great way to work but need concentration on how to use it.
when the page is finished. My modules stay alive (as long as the application is not ended or restarted) and I can reuse the data in it.I use this to save data that sometimes is lost because of the sessionhandling by IIS.
The various answers in this blog seem to be defined by SE's who promote strict adherence to the usual rules of object-oriented programming (use a Public Class with public shared (aka static), and fully-qualified class references, or SE's who promote using the backward-compatibility feature (Module) for which the compiler obviously needs to do the same thing to make it work.
If you are writing all new code (not attempting to convert a legacy app) that you avoid using these forms altogether except in the rare instance that you really DO need to have a static variable because they can cause terrible consequences (and really hard-to-find bugs). (Multithread and multiprocessing code requires semaphores around static variables...)
If you are modifying a small application that already has a few global variables, then formulate them so they are not obscured by Modules, that is, use the standard rules of object-oriented programming to re-create them as public static and access them by full qualification so others can figure out what is going on.
If you have a huge legacy application with dozens or hundreds of global variables, by all means, use Modules to define them. There is no reason to waste time when getting the application working, because you are probably already behind the 8-ball in time spent on Properties, etc.
The first guy with a public class makes a lot more sense. The original guy has multiple forms and if global variables are needed then the global class will be better. Think of someone coding behind him and needs to use a global variable in a class you have IntelliSense, it will also make coding a modification 6 months later a lot easier.
There are lots of string variables in the visual basic code of forms used to customize dynamos. I have searched every project and I can't find where they are declared. They are variables like sDynamoName, sFriendlyName, strOKButton, etc. They must be public, since I can't find them in local declarations or subroutine calls. Does anyone know where I can find these? I would like know what variables exist and what are their values. I can't view the FactoryGlobals, frsFactoryGlobals or frsDevAlm projects. Perhaps that's were they come from.
A basic description of a global variable is one that, once declared, it belongs to no instance in particular and yet can be accessed by all. Just like local variables, global variables must be declared using an identifier, but unlike a local variable, a global variable remains in memory until the end of the game. So, you can create a global variable to keep track of (for example) the number of bullets that the player has and then just update this variable at different points in the game, form any instance or function and at any time. Essentially, a global variable does not belong to any specific instance and can be accessed, changed and used by all instances, and any changes made to the variable are "global", in that all instances using the variable will be affected by the change. Let's have a look at an example:
We declare the "food" variable by first writing "global" and then a "." to tell GameMaker that this variable is now global scope. We will need to use this form from now on any time we are required to access or to change this variable in any way. So, we have created a new variable called "food" and we have declared it as global. Now, any instance or function can use and change this variable in any way and all other instances will "see" this. For example we could have a different food object that the player collides with and in the collision event we have:
With global variables we can change values and see those changes reflected in all instances of the objects that reference this variable. As with local variables you have to take care not to name your global variables the same as any instance variables as that may cause you problems and make bugs creep into your games due to variable overlap, which can be a difficult issue to debug sometimes. In general you should have a single object that declares all your global variables at the very start of the game (for example, in the Room Start Event of the first object instance placed in the first room of the game) or a single script function that declares them all together, as this gives you a handy place to go back and reference everything at once should you need to check a variable name or edit a value.
GameMaker has a collection of "built in" global variables too, so you should be aware of them as you may name one of your instance variables the same or wish to have your own global variable with the same name and wonder why you are getting errors! They are easy to spot, however, as they are shown in a different colour in the code editor and also come up in the auto-complete bar at the bottom. The majority of built-in global variables have very specific uses are listed in the appropriate sections of the manual - however there are two important ones that are used frequently and aren't listed elsewhere:
There are also three deprecated built in global variables which you should be aware of (these variables are only designed to support legacy projects from previous versions of GameMaker and should not be used in new projects):
The following form can also be used to declare global variables, but it is only included for backwards compatibility, and it is not recommended that you use this form for new projects as future versions of GameMaker may not support it.
Once declared in this way that variable "food" is now considered global and requires no global. prefix - which also means that it's a lot harder to identify global variables in your code and it's also much easier to get variable overlap as you use the same variable name in different objects or from extensions that you've installed. Once declared in this way the global variable is accessed as follows:
As you can see, with nothing to show that the variable is global in scope you are potentially setting yourself up for many subtle problems to arise in your game, which is why this declaration should be avoided.
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