global versus local versu temporary variable

[Jen0dorf]

Hi

am changing my database to use new knowledge gained - thanks one and all.

Can I just confirm that a global variable remains as long as the database is open.

A local variable remains as long as the form is open

A temporary variable is used for temporary items within a set sequence of actions

To explain my project is now becoming for me rather large.

At the top of each form is one of two text sequences and I though I could create a form to hold the text in fields and then on database load create global variables to hold the values. The call these values into each form.

Then when the secretary or phone number or anything changes I only have to change one line.

I though a global variable was the way to go????

thanks



Ian

[davegri]

A local variable remains as long as the form is open

Not quite that broad. A variable dimmed in a procedure (a sub or a function) is valid only within that procedure WHILE THAT PROCEDURE IS EXECUTING.
You might also look into Tempvars for holding global values. Tempvars can be defined on the fly in code, while global constants have hard coded values.

[CJ_London]

A global variable - that is one declared as Public at the top of a module

- will remain available to the entire code whilst the code is running if declared in a standard or class module
- will remain available to the entire code whilst the form is open if declared in a form module
- you cannot declare a public variable in a function or sub
- it will lose any values if you have an unhandled error

A tempVar is similar but will retain its value if you do get an unhandled error
- it also has the benefit it can be referenced in a query

A local variable - one that is declared with Dim or Const
- will remain available to the code for the life of where it is declared, be it a function/sub/form or report
- it will lose any values if you have an unhandled error

A Static variable - one that is declared with Static
- can only be declared in a function or sub
- so is only available to the code in that function or sub
- like tempvars it retains its value if you get an unhandled error

For functions and subs you can declare them as public (the default if not declared) or private
in terms of availability to other code, public is the equivalent of a global variable and private a local variable


you might find this link useful

https://www.youtube.com/watch?v=KxzoDFxX9As

[June7]

while global constants have hard coded values.

Variables can be reset, constants cannot. Examples:

Global gstrArrayTestMethods() As Variant

Global Const gstrBasePath = "C:\Crm\Lab\Database\"

Public Const PI As Double = 3.14159265358979

[ssanfu]

Then when the secretary or phone number or anything changes I only have to change one line.

You might consider using a table, maybe name it "GlobalConstants" or "GlobalData", rather than put it (secretary or phone number or anything) in code. In a table you can use a form to easily change the data; in code you have to go into design view. You can still use code to fill global variables, tempVars, whatever.

It works for me......




My $0.02 ..........

[CJ_London]

My $0.02 ..........

and worth every cent. Had only focused on the definitions, not the way it is intended to be used

[Jen0dorf]

You might consider using a table, maybe name it "GlobalConstants" or "GlobalData", rather than put it (secretary or phone number or anything) in code. In a table you can use a form to easily change the data; in code you have to go into design view. You can still use code to fill global variables, tempVars, whatever.

It works for me......




My $0.02 ..........

Thanks think thats the way I'll go

cheers

Ian

[CodeLiftSleep]

I create globals for use as Singleton's---for instance if I have a loggedInUser Class with various properties like UserID and UserName, etc, I'll create a "GlobalFunctions" module and create a single instance of this class as something like:

Public loggedUser as New LoggedInUser

And since we only have one of these at any time in a program, this object can be referenced from anywhere in code...this is similar to creating a Public Static Class in C# to use as a Singleton, since you don't want to actually create an instance of it, simply be able to use it...in this case we have to create a single instance of it due to VBA limitations, but then use the instantiated object like its a Singleton.

I also use it for creating FilePath strings to reference from anywhere.