Global variables in a Lazarus service (TDaemon)

[TyneBridges]

I'm creating a Windows service with a lot of help from forum members. I need to pass a value returned by the DaemonMapper to DaemonUnit1. I understand that any variable declared with var in the Interface section should be global in scope. However, no matter whether I put the

Code: Pascal  [Select][+][-]

1. var NMsg: String;

in the Interface of DaemonMapperUnit1 or in the same section of DaemonUnit1, I get "Error: identifier not found" when I try to compile.

I understand that it should be in whichever unit is initialised first, but I've tried it in both and it works in neither. Any ideas?

Thanks.

[lucamar]

This is very basic so excuse me if you already knew, but ...

You have to add the unit in which it's declared to any other unit who uses it. You do this by adding the unit's name to the uses  clause:

Code: Pascal  [Select][+][-]

1. unit unit1;
2. interface
3.   var somevar: string;
4. implementation
5. end.
6.  
7. ----------
8.  
9. unit unit2;
10.  
11. interface
12.   {... whatever ...}
13.  
14. implementation
15.  
16. uses unit1;
17. procedure SomeProc;
18. begin
19.   somevar := 'soemthing or other';
20. end;
21.  
22. end.

Do note that "global in scope" in this case just means it's global in the unit in which it's declared (that's the "scope") as opossed to a function-local var  or a variable (or const/type) declared only in the implementation section.

Declaring something in the "interface" allows you to refer to it elsewhere (i.e. other units) but you must declare "elsewhere" where it should be searched for, in the uses clause.

[TyneBridges]

This is very basic so excuse me if you already knew, but ...

You have to add the unit in which it's declared to any other unit who uses it. You do this by adding the unit's name to the uses  clause:

Thanks! I used to know that but it's so long since I started any new projects that I'm having to re-learn some of the basic stuff. I should have realised, but I'm grateful for your help.

[lucamar]

Glad to be of help

[PascalDragon]

I'm creating a Windows service with a lot of help from forum members. I need to pass a value returned by the DaemonMapper to DaemonUnit1. I understand that any variable declared with var in the Interface section should be global in scope. However, no matter whether I put the

Code: Pascal  [Select][+][-]

1. var NMsg: String;

in the Interface of DaemonMapperUnit1 or in the same section of DaemonUnit1, I get "Error: identifier not found" when I try to compile.

What exactly are you trying to forward? Maybe there is a better method to do this than a global variable.

[TyneBridges]

I'm creating a Windows service with a lot of help from forum members. I need to pass a value returned by the DaemonMapper to DaemonUnit1. I understand that any variable declared with var in the Interface section should be global in scope. However, no matter whether I put the

Code: Pascal  [Select][+][-]

1. var NMsg: String;

in the Interface of DaemonMapperUnit1 or in the same section of DaemonUnit1, I get "Error: identifier not found" when I try to compile.

What exactly are you trying to forward? Maybe there is a better method to do this than a global variable.

Thanks. I was trying to get the value returned by the service in a control event to my log file created in the other unit. It turned out that I had the control event code in the wrong unit anyway (see my logon/logoff service thread) and even simplified code has other problems...