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MT4 global variables: my new best friend

  • #21
  • Nov 20, 2010 2:56pm Nov 20, 2010 2:56pm
I'm not familiar with what you are talking about. Can you show me?

Quoting 7bit
prepend the name in your gvg() function with

WindowExpertName()+Symbol()+Period()

and you will have them always nicely (and automatically) separated for each EA on every chart and timeframe with even less typing.

See my other example above. You basically repeated my example but you left out the neat part where the magic happens that *really* saves a lot of typing and coding.
  • #22
  • Nov 20, 2010 3:13pm Nov 20, 2010 3:13pm
Quoting tdion
I'm not familiar with what you are talking about. Can you show me?
Inserted Code
[color=#7f0055][b]string[/b][/color] [color=#000000]getFullName[/color][color=#000000]([/color][b][color=#7f0055]string[/color][/b] name[color=#000000]){[/color]
   [color=#7f0055][b]return[/b][/color][color=#000000]([/color][color=#000000]WindowExpertName[/color][color=#000000]() +[/color] [color=#000000]Symbol[/color][color=#000000]() +[/color] [color=#000000]Period[/color][color=#000000]() +[/color] name[color=#000000]);[/color]
[color=#000000]}[/color]

[color=#7f0055][b]void[/b][/color] [color=#000000]setVariable[/color][color=#000000]([/color][color=#7f0055][b]string[/b][/color] name[color=#000000],[/color] [color=#7f0055][b]double[/b][/color] value[color=#000000]){[/color]
   [color=#000000]GlobalVariableSet[/color][color=#000000]([/color][color=#000000]getFullName[/color][color=#000000]([/color]name[color=#000000]),[/color] value[color=#000000]);[/color]
[color=#000000]}[/color]

[color=#7f0055][b]double[/b][/color] [color=#000000]getVariable[/color][color=#000000]([/color][color=#7f0055][b]string[/b][/color] name[color=#000000]){[/color]
   [color=#7f0055][b]return[/b][/color][color=#000000]([/color][color=#000000]GlobalVariableGet[/color][color=#000000]([/color][color=#000000]getFullName[/color][color=#000000]([/color]name[color=#000000]));[/color]
[color=#000000]}[/color]
If you have an EA that is called "foobar.mq4" and is running on EURUSD M15 and you call the function like this:

setVariable("something", 42);

it will create a global variable that is named"foobarEURUSD15something". If you run the EA on a different chart or use this function in another EA it will create a different name for the variable. Now you can have a "something"-variable in each of your EAs without ever having to worry about possible collisions. Each EA and each instance of the same EA will have its very own namespace for its global variables.
  • #23
  • Nov 20, 2010 3:17pm Nov 20, 2010 3:17pm
Ah, clever
  • #24
  • Edited 3:26pm Nov 21, 2010 2:58pm | Edited 3:26pm
Quoting 7bit
For magic numbers I use a hash over name+symbol+timeframe, this is more robust and needs no persistence layer. For global variable names a string will work, no need to convert this to a number (but of course one could use the (auto-generated) magic-number for this too if it already exists).

a hash would generate the same magic number;

system name, symbol, and time frame, are mainly strings which are fine for globals and objects but will not work for magic numbers, and what about the different days you run the same system on the same timeframe and symbol? with a different controlID and ProgramID I can not only keep performance logs of each run but each order in that run. the orders are tracked by the order tracking number. Which is the controlId and the ProgramId numbers multiplied by 100. so inthe case of my last post the ordertracking number was 67122513 then multiply by 100 would add two zeros.... 6712251300. so the first order of that run is 6712251301 the second 6712251302 and so forth, each order has a different magic number but the same runtime number, each order therefore can be tracked and your perforamance as a trader can be documented. now if I trade more then once in a given day with the same system same currency pair on the same timeframe Both will have different runtime serials numbers and all canbe traced seperatly.

If you care to take a careful look at my object nameing you will see that there is a method there. why? I can not only delete all objects that belong to a given program but I can also limit my deletions, by group name, all that fall within a given window, by class, or sub class and just one by name. the only limit is that one program can not delete another programs objects or globals nor manage others orders. How ever the controller overlay program has the ability to override that. therefor I can run the same system, onthe same sysbol, on the same timeframe at the same time (if I wanted too) and be able to keep everthing correctly logged.

The controller overlay program is the program that looks over all other programs linked to it by the 'shared: object'. It is also the means that the user communicates with the system. the controller accepts user imputs (in a number of ways) and passes it on to the correct program(s).

This is more robust to me;

Keit

edit; If you look at the small camra in one of the above posted screen shots; that instructs the controller to take screen shots of the platform on every order open and close. on every trigger even if you donot take that a position, along with other things. these are labeled in the same means which means that you can go back and study your trading form.
Trader Keit ... Methods Of A Dirt Road Mad Man....
  • #25
  • Nov 21, 2010 3:15pm Nov 21, 2010 3:15pm
Quoting CockeyedCowboy
what about the different days you run the same system on the same timeframe and symbol?
I always want the same magic for the same EA on the same symbol and timeframe. This is what magic numbers are usually used for.

It must be able to immediately pick up the old trades and continue seamlessly even if I install it on a completely new computer. This is my requirement and most likely also the requirement of most others. If you need different IDs for different runs then you can additionally include a variable that uniquely identifies each separate run or each separate parameter set in the hash.
  • #26
  • Nov 21, 2010 3:28pm Nov 21, 2010 3:28pm
Quoting 7bit
I always want the same magic for the same EA on the same symbol and timeframe. This is what magic numbers are usually used for.

It must be able to immediately pick up the old trades and continue seamlessly even if I install it on a completely new computer. This is my requirement and most likely also the requirement of most others. If you need different IDs for different runs then you can additionally include a variable that uniquely identifies each separate run or each separate parameter set in the hash.
I can do the same thing;
Trader Keit ... Methods Of A Dirt Road Mad Man....
  • #27
  • Mar 28, 2011 12:36am Mar 28, 2011 12:36am
I tried using Global Variable but it is not working.


GlobalVariableSet(TakeOver,1);

if (GlobalVariableGet(TakeOver) == 1)
{
TradeTakenOver = true;
}

Comment(TradeTakenOver);


TradeTakenOver should show as 1 but it still shows as 0.
  • #28
  • Mar 28, 2011 1:09am Mar 28, 2011 1:09am
Quoting mindreality
I tried using Global Variable but it is not working...........
The code below works fine for me. The comment value that is output is 1.
Inserted Code
  bool TradeTakenOver = false;
  string TakeOver = "TakeOver";
  GlobalVariableSet(TakeOver,1);
  if (GlobalVariableGet(TakeOver) == 1)
    TradeTakenOver = true;
  Comment(TradeTakenOver);

Perhaps you didn't define TakeOver as a string?
  • #29
  • Mar 28, 2011 1:44am Mar 28, 2011 1:44am
Quoting hanover
The code below works fine for me. The comment value that is output is 1.
Inserted Code
  bool TradeTakenOver = false;
  string TakeOver = "TakeOver";
  GlobalVariableSet(TakeOver,1);
  if (GlobalVariableGet(TakeOver) == 1)
    TradeTakenOver = true;
  Comment(TradeTakenOver);

Perhaps you didn't define TakeOver as a string?
Thanks!

I made the mistake of

string TakeOver;

I should have added the

= "TakeOver";
  • #30
  • Edited 5:33pm Dec 11, 2011 4:11pm | Edited 5:33pm
Hi guys, I am rather new to mql4 and have been reading up about global variables.

Just wanted to check with you guys to be sure i understand it,

1) Values stored as global variables are on mt4 terminal itself?
2) they are stored for a maximum of 4 weeks from input
3) What happens if the mt4 terminal crashes or OS crash or a power glitch, will the data stored as global variables be lost?

Hope you guys can clarify these for me.

Thanks for the help.
  • #31
  • Dec 11, 2011 5:28pm Dec 11, 2011 5:28pm
Quoting denialyg
Hi guys, I rather new to mql4 and have been reading up about global variables.

Just wanted to check with you guys to be sure i understand it,

1) Values stored as global variables are on mt4 terminal itself?
2) they are stored for a maximum of 4 weeks from input
3) What happens if the mt4 terminal crashes or OS crash or a power glitch, will the data stored as global variables be lost?

Hope you guys can clarify these for me.

Thanks for the help.

1) I believe they are stored in the magical realm... somewhere within your computer. Guarded by green clovers, lucky charms and a mean little leprechaun.

2) they are stored for a maximum of 4 weeks (without being accessed).
So as long as you are accessing the GV it will never be unstored. It would only stop storing the information if you never accessed the information again within 4 weeks. (There is nothing that I know of that beats a GV.)

3) If your computer crashes and burns... yeah you got bigger problems than GV's. But just having to reboot from a system crash? no worries... the GV will remember once you reboot and start the terminal back up.

Just remember you have to have a test to make sure the GV doesn't exist and create one if it doesn't, a string name for the GV and then assign a value to it. You have to set the GV somewhere within the code and you have to get the GV value somewhere within the code. It's best to position these toward the top so it gets accessed on every tick or whatever requirements you set for them to get accessed and / or reset them.

If you access them on nearly every tick you never have to worry about a GV expiring. 4 weeks is a long time. Even I have trouble remembering stuff after 24 hours... and I reboot myself every day, sometimes more than once. LOL

If you do it right GV's are very powerful memory retaining controls for your EA.
  • #32
  • Dec 13, 2011 7:08am Dec 13, 2011 7:08am
Thanks for clearing the air for me.
  • #33
  • Oct 4, 2015 10:06pm Oct 4, 2015 10:06pm
I read that Global Variables values can be shared between EA's

I am running the same EA on different charts.

My requirement is to execute only maximum one trade signal in one BAR among all the EAs.
Meaning if one trade is executed on any of the chart then do not execute the signal on another chart on the same BAR.

I am trying to achieve this via GLOBAL variables by so far not successfull.

Can someone help me please to achieve this ....
  • #34
  • Jan 10, 2021 6:05am Jan 10, 2021 6:05am
F3 and change ?
  • #35
  • Last Post: Jun 2, 2022 7:33pm Jun 2, 2022 7:33pm
Quoting lohikeitto
Here is a sample code. //+------------------------------------------------------------------+ //| Global Variables test //+------------------------------------------------------------------+ /* MetaEditor's explanation datetime GlobalVariableSet( string name, double value) Sets a new value of the global variable. If it does not exist, the system creates a new gloabl variable. If the function succeeds, the returned value will be the last access time. Otherwise, the returned value will be 0. To get the detailed error information, one has to call the...
Thank you very much. You just saved me a stress
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