Sharing variables between apps

hello,
i have 2 apps with one being a background tool for the main app. is it possible to pass along variables from the background app to the main app? maybe some kind of global variable? i'm thinking also distributed objects might be the way to go but i have never done this before so i thought i'd ask for some input. thank you very much,
rick

rick722 wrote:
thank you both for the replies and glad to hear there's options. to be a bit more specific both apps are mine so i don't really need to pass info to other apps. and yes it's just for mac os x. basically the small background app is monitoring a directory for changes. when a change occurs it does some basic processing to see what the changes were and then if necessary it will launch/activate my main app and hopefully provide info regarding the changes.
Before you get too deep into it, have you looked at FSevents? fseventer is a good example.
in this case it's really just the filenames i'm interested in so passing along an array of filenames would probably do the trick. and it would generally be a small array maybe 10 to 15 objects on average. i don't believe i will need communication back to my background app it would be one-directional.
Are you sure you need a background app? You can write an app the stays hidden until you need it.
As far as communication goes, you have lots of options. You could use something like a unix domain socket and just use standard file I/o. A pipe or named pipe would be very similar. Your background app could be a pure POSIX app. If your background app includes Cocoa, you could use NSDistributedNotification.
as an example the kind of behavior i'm looking for is like when you drop files onto the dock icon of apps that have an application:openfiles: method and the app will receive an array of filenames. except in this case i want to pass the array from my background app. thank you both for the help.
Another option is to just have your GUI app handle the open file AppleEvent (a standard document-based app) and the background app could send open file events to the GUI.
Finally, someone else mentioned using launchd.

Similar Messages

Problem Sharing Variables between 2 machines

I am having problems trying to create a project that would share variables between multiple computers. I am using Labview 8.2.1 (I am new to 8.2.1 and Shared Variable).
here is what i did:
1. I created the project with Client and Server VI's and a library containing shared variables, which both of them call
2. I placed this project onto 2 computers (XP on a local workgroup, no firewall, see each other).
3. On one of the computers I bound all shared variables to their counterparts on the other computer
The system is "almost working"
The problems are:
- I initially used wrong type variables for few items. I then modified the variables in both VI's and Shared Variable libraries and repeated the Steps 1-3 above.
But the sysrtem has some sort of a buffer somwhere, because it keeps bringing the old types of shared variables back (when I monitor them using Shared Variable Monitor).
- When I do binding to source, the system shows wrong variable types (for example DBL instead of U8).
- It takes almost a second to write and read shared variable (my network is quite fast)
I saw that the Labview Example with Server and multiple Clients uses 2 sets of shared variable and they bind - separate sets (different names) fro client and server within the same project. Do I have to do this or is this done just to simplify bindinga nd future distribution?
Is there a buffer/setup/file that I need to clear to get rid of "old" shared variable assignements? (I tried undeploy/deploy - does not help...)
Thank you very much,
Gleb.

Hi Gleb,
It sounds like the shared variable is not getting completely undeployed from the shared variable engine. I would recommend opening the shared variable manager and undeploying the library from there just to see that it is no longer in the engine. Then, redeploy the library and rebind your variables to the host library that you have deployed.
It is not necessary to have different sets of variables for client and host. The important part of the variable is what it is bound to, not necessarily what it is named. So just undeploy your variable, double check the settings of the host variable, then redeploy using the variable manager and rebind your client variables.
I hope this helps,
Brian Coalson
Software Engineer
National Instruments

How you connect a shared variable between internet?

Hello;
I have a aplicarían which use the shared variables, and other one which is the slave. both work rightly, in a local lan, but now I need connect the slave aplication between Internet.
what is the procedure?????
thanks in advance

Hola Joju,
La tecnología de variables compartidas sólo es válida dentro de una red local. Si necesitas acceder a una variable desde Internet, tendrías que hacer uso de DataSocket y de servidores DNS.
Servidores DNS para que tu PC tenga asociado un dominio en Internet y, de esta forma, se pueda acceder a él a través de su nombre. El problema es que tendrías que dar de alta dicho dominio. Después, seguir las instrucciones de este link, cambiando direcciones IP por nombres de equipo:
How to Use Shared Variables and DataSockets to Pass Data Between Two Networked PCs
Esto no es trivial y dependiendo de la configuración de la red del operador, es posible que haya problemas. Para comunicación a través de la red, siempre es más recomendable utilizar funciones básicas de TCP/IP o servicios web.
Un saludo,

How do I setup shared variables between executables created in sepparate projects

Hello,
I have several sepparate projects with their own respective executable files and I would like to be able for these executable files to all share the same variable (one program controls the value of the variable, while the others read from it).
I got this setup to work on my personal computer (by being able to access variable manager, etc), but I need to deploy these executables on different computers that don't have the labview development program. What steps do I need to do in order for me to be able to put these executables on any computer (I'm assuming I need to setup a path for the shared variable that is always in the same folder, etc)
Thanks
Vlad
Solved!
Go to Solution.

Hi Vlad,
I think this article may answer some of your questions regarding shared variables in deployed applications.
http://zone.ni.com/devzone/cda/tut/p/id/9900
It sounds like you already have your executables built, but this article may answer some questions about deploying them to other machines.
http://zone.ni.com/devzone/cda/tut/p/id/3303
Jeff S.
National Instruments

Sharing video between Apps

Hi there. I have a home video edited in iMovie on my Mac and transferred to the Apple Video App on my iPad (iOS7). I would like to share this video with another app, "Write-on Video". This latter app will only import material from the iPad camera, the Evernote app (which also doesn't have an option to import video in its controls), and the internet. Apparently, it is nonetheless possible to save video into the Evernote app through the "share" option on apps, only the Apple Videos app doesn't seem to have a "share" option. Does anyone have an idea about how I might get my video into the Write-on Video app?
NB I really don't like the way each app is its own little island and how transferring material between them can't just be drag-and-drop (as long as the file types match) and has to involve various complicated juggling acts.

Hi pogo. Thanks for the response.
Unfortunately, this approach is exactly what I have a problem with. I seems counterintuitive. A specialized app needs to be made and then bought, for each simple thing like this. I already paid for the overpriced Pages. And now I have to pay for documentstogo and hope that it does what I want? I'm trying out An app at the moment called plaintext to see if this will do it for free...
BUT, my original point still stands. I was hoping to generate a little discussion on what I see as a limitation of IOS. Something that seems so simple is such an issue. I sortof see why apple has chosen to keep us away from the file system. But I think the cost is too high. Apple, give us a 'personal' chunk of the file system that we/apps can have SHARED access to. Then maybe IOS devices really can be more than just a toy.
Another example: last night, on my android phone, I downloaded an mp3 from my browser, then opened the file manager app, moved it to the media folder, and then set it as my ringtone. No need for a PC, ever. I fail to see how anything remotely close to this level of convenience is possible on an apple Device.
Cheers,
James

'Sharing' Files Between Apps?

This may be a fools' errand.
Since the days of Palm Pilots, I've been using Docs to Go pretty heavily.
I sync most of my files through my Desktop, not the cloud.
Now, I'm attempting to trial-run some good PDF annotation apps. I have a bunch of PDFs that I've synced between my Desktop and my iPad with Docs to Go.
Is there any way I can open that same file using, say, GoodReader? Or do I need to push a copy of the same PDF into GoodReader with iTunes? (And then of course, I'll lose version control between the two apps...?)
Or... what other options do I have?
Thanks

If DocumentsToGo shows your other Apps in the Open in.... menu, you won't need to push another copy. However, you're never really going to be able to share documents the way you want. You'll essentially have two copies.
By the way, I find, unless the documents are quite large or you have lots of them, emailing them to yourself is easier than iTunes. I believe you can email from Documents to Go.
I've forgotten if Documents to Go supports DropBox. If it does, you could store the apps their and open from GoodReader.
Best of luck.

Sharing variables between classes

Hi,
I wrote a class to handle button functionality. I want the
onPress event in this class to play a movieclip that is sitting in
my .fla file, also access some boolean values in the .fla.
What's the best way to implement this?

Best practice is to avoid directly accessing non-static final fields of other classes - they should generally by private or if necessary protected.
get/set methods are the usual way to do this. You can use public static final fields without having a getter.
Static in the context of field definition identifies fields which exist at the class scope (1 copy per class) versus those (non-static) which exist at the instance scope (1 copy per instance of the class).
If the value you want to share instance-speciifc, use a non-static field backed up by non-static get/set methods. If you want one copy per process, static fields with static get/set methods are best.
Chuck

Sharing variables between 2 custom components. Please help.

Hi,
I'm a beginner in java and I have a problem. I'm using Netbeans 5.5.1
I need to use 2 classes, defined in 2 separate files, in a third, main class.
Actually I copy/paste the 2 classes (are made as swing jpanels with controls, textboxes, combos, etc) in the main class, so in the main class they appear as components.
what I need is to read a combo box from first component every time when it is updated and use it in second component , when a buton from second component is pushed.
I don't know haw could this be done.
Thanks,
Dan

http://en.wikipedia.org/wiki/Model-view-controller
What you need is a controller. Let your gui classes do nothing but interact with the user and tell the controller class when they do something (like push the button on the second component). Then the controller gives the guis their updated data to display.

Communicating Between Multiple LabVIEW Executables on different computer using Shared Variables

hi,
I need to develop some executables which will be launched on different computer of a LAN. Some DATA are common. I need to share the data using shared variables.
I usually used LabVIEW so I 'm familiar with shared variables but in this case, the RT target is a part of my
project.
I do I need to procceed in my case?
thanks

Ok but it's not my configuration and I haven't found my answer in the tutorial.
You speak of a case where there is a computer and a RT target under the same LabView project. As I said earlier, I often use labview RT and shared variable between computer and RT target. But I assume here it's different.
My question is : how do you acces to the SVE from 3 computers (without any RT target)?
1. If I create 3 labview projects using the same Shared Variable, do I need to use the same .lvlib on each project?
2. Is it possible?
3. How can I configure where the SVE should be? When I use a RT target, It only depends where I put my Lvlib. But here there is 3 projects.
James
Attachments:
Sans titre.JPG ‏9 KB

Peculiar behavior of Shared Variable RT FIFO

I'm trying to "leverage" the enhanced TCP/IP and Shared Variable properties of LabView 8.5. My application involves (among other things) doing continuous sampling (16 channels, 1KHz/channel) using 6-year-old PXIs (Pentium III) and streaming data to the host. I developed a small test routine that was more than capable of handling this data rate, even when I had the host put a 20msec wait between attending to the PXI (to simulate other processing on the host). To do this, I enabled the "RT FIFO" property of the Shared Variable (which was an array of 16 I16 integers) and specified a buffer size of 50 (that's 50 arrays). Key to making this work was figuring out the "error codes" associated with the SV RT FIFO, particularly the one that says the FIFO is empty (so don't save the "non-data" that is present).
Flush with success, I started developing a more realistic routine that involves rather more traffic between Host and Remote, including the passing back and forth of "event" data. These include, among other things, "state variables" to enable both host and remote to run state machines that stay "in sync"; in addition, the PXI also acquires digital data (button pushes, etc.) which are other "events" to be sent to the Host and streamed to disk. I developed the dual state-machine model without including the "analog data" machine, just to get the design of the Host/Remote system down and deal with exchanging digital data through other Shared Variables. Along the way, I decided to make these also use an RT FIFO, as I didn't want to "miss" any data. One problem I had noticed when using Shared Variables is the difficulty of telling "is this new?", i.e. is the variable present one that has been already read (and processed) or something that needs processing. I ended up adopting something of a kludge for the events by including an incrementing "event ID" that could be tested to see if it was "new".
Today, I put the two routines together by adding the "generate 16-channels of integer data at 1 KHz and send it to the Host via the Shared Variable" code to my existing Host/Remote state machine. I used exactly the same logic I'd previously employed to monitor the RT FIFO associated with this Shared Variable (basically, the Host reads the SV, then looks at the error code -- a value of -2220 means "Shared Variable FIFO Read Buffer Empty", so the value you just read is an "old" value, so throw it away). Very sad -- my code threw EVERYTHING away! No matter how slowly the Host ran, the indicator always said that the Shared Variable FIFO Read Buffer was empty! This wasn't true -- if I ignored the flag, and saved anyway, I saw reasonable-looking data (I was generating a sinusoid, and I saw numbers going up and down). The trouble was that I read many more points than were actually generated, since I read the same values multiple times!
Looking at the code, the error line coming into the Shared Variable (before it was read) was -2220, and it remained so after it was read. How could this be? One possibility is that my other Shared Variables were mucking up the error line, but I would have thought that the SV Engine handling reading my "analog data" SV would have set the error line appropriately for my variable. On a hunch, I turned of the RT FIFO on the two Event shared variables, and wouldn't you know, this more-or-less fixed it!
But why? What is the point of having a shared variable "attached" to an error line and having it return "Shared Variable FIFO Read Buffer Empty" if it doesn't apply to its own Read Buffer? This seems to me to be a very serious bug that renders this extremely useful feature almost worthless (certainly mega-frustrating). The beauty of the new Shared Variable structure and the new code in Version 8.5 is that it does seem to allow better and faster communication in real-time using TCP/IP, so we can devote the PXI to "real-time" chores (data acquisition, perhaps stimulus generation) and let the PC handle data streaming, displays, controls, etc.
Has anyone been successful in developing a data-streaming application using shared variables between a PXI and and PC, particularly one with multiple real-time streams (such as mine, where I have an analog stream from the PXI at 16 * 1KHz, a digital stream from the PXI at irregular intervalus, but possibly up to 300 Hz, and "control" information going between PC and PXI to keep them in step)? Note that I'm attempting to "modernize" some Version 7 code that (in the absence of a good communication mechanism) is something of a nightmare, with data being kept in PXI memory, written on occasion to the PXI hard drive (!), and then eventually being written up to the PC; in addition, because the data "stayed" on the PXI, we split the signal and ran a second A/D board in the PC just so we could "see" the signal and create a display. How much better to get the PXI to send the data to the PC, which can sock it away and take samples from the data stream to display as they fly by on their way to the hard drive!
But I need to get Shared Variables (or something similar) working more "understandably" first ...
Bob Schor

Bob,
The error lines passed into and out of functions are just just clusters with a status boolean, an error code, and an error string, and are not "attached" to a particular function as you describe in your post. Most functions have an error in input and an error out output, and most functions will simply do nothing except pass through the error cluster if the error in status is True (to verify this for yourself, double click on a function such as a DAQmx Read or Write and look at the block diagram. If there is an error passed in, no read/write occurs). This helps prevent unwanted code from executing when an error does arise in your program. By wiring the error cluster from your other shared variables to your analog data variable, you're essentially telling LabVIEW that these functions are related and that your analog data variable depends requires that the other shared variables are functioning properly. The error wire is a great way to enforce the flow of your program, but you must always consider how it will affect other functions if an error does arise.
Anyways, it's great that you have things more or less working at the moment. Keep us all updated!

Using Shared Variables and Initialize Front Panel Binding (to PSP)

Hi,
I use LV DSC RT 8.2.1
I have a Vacuum System That includes signals from - Pumps failure, Valves status, Vacuum gauge, start Pump ...
Each signal is read by a FieldPoint.
All the relevant FieldPoint Channels are read by the Server (a computer in the Ethernet Network) and published to the network in the form of Shared Variables.
I have a client VI that is reading the Shared Variables published by the Server using Front Panel Binding.
Problem :
Some of the Bindings are in the mode 'Write &Read' and that causes some initialization problems.
For example - Valve #1 is Open, and then a User start running the Client VI, (the Valve #1 Status mode is 'Write & Read")
if in the VI the status of Valve #1 is closed (before running it) then the Valve status is changing to Closed.
I want the Client VI to first read the Physical status of the instrument and then to change the Value if the User changes it.
But that's seems to be a problem when using Front Panel Binding... (is it?)
I know I can Deploy a lvlib in the Client Side and Item Bind to the Shared Variables or Use DataSocket.
(Is DataSocket is a Reliable method when connecting to Shared Variables? What are the disadvantages when using DataSocket?)
What is recommended by those of you that are experienced or by NI ?
Sincerely Yours,
Amitai Abramson.

Amitai Abramson,
Hello and thanks for using the NI Forums.
I'm glad that you've read the Using the LabVIEW Shared Variable Tutorial on our website. Check out these other resources:
Network Variable Technical Overview
Troubleshooting Network-Published Shared Variables
Why Do I See Unexpected Value Change Events for Shared Variables Using LabVIEW DSC?
All You Need to Know About Shared Variables
Creating a Value Change Event for Shared Variables
Alternative Method for Using Shared Variables Between Systems in LabVIEW 8.x
What Is The Difference Between Using Shared Variables And DataSocket VIs To Access OPC Tags?
The issue that you are seeing by having "Write & Read" bound items on both the server and client side is essentially a race condition, you don't know which one is being read/written at what time. To resolve this issue I would take a look at some of the documents below.
Using a Local, Global, or Shared Variable in Parallel Loops Can Cause Race Conditions
Using Local and Global Variables Carefully
Tutorial: Local Variable, Global Variable, and Race Conditions
Locking a Shared Resource or Variable in LabVIEW Using Semaphores
You mentioned not wanting to have two sets of shared variables (one on each side), but this is a great method to resovle this issue, that, or you can develope some sort of hand shaking to prevent these race conditions.
I would suggest that in the future when using these forums you try to ask only one question per thread and make it more concise. It's hard to tackle multiple questions and such broad questions as "I want to know all the ways that I can connect to Shared Variables, and I want to know the advantages and disadvantages." I suggest this because we want you to get your questions answered and more concise questions will result in quicker and better answers.
Message Edited by Ben S on 10-01-2009 06:05 PM
Ben Sisney
FlexRIO V&V Engineer
National Instruments

Shared Variable Engine on Windows PC w/o full install of LabVIEW

I have the NI Developer Suite (8.20) and need some conformation before I get too deep in a project.
First of all, it is my desire to become very efficient on develop compiled executables with LabVIEW 8.20 as my NI Developer Suite license allows me to deploy these programs to any number of machines without facing copyright infringement. I have been successful with this to a certain degree, but am still having problems in the testing stages of my application especially in cases where the hardware I am trying to target does not exist on my developing station. If anyone can point me to white papers that would help me get the mindset to develop in this way, I would appreciate it.
Onto the topic of this post:
I am just scratching the surface of the shared variable interface that is available in LabVIEW 8.2. My project involves two computers where both of them need to share variables back and forth from each other. I've been reading everything I can get my hands on and I am having a hard time answering my unlying question: Is it possible for both of these machines to be running compiled LabVIEW programs and still manage the shared variables between them? That is to say, can one of the machines have the Shared Variable Engine running on it as a Windows service, or compiled into my application executable.
I've read that I can access shared variables from my compiled LabVIEW application through NI-PSP. I am wondering what my limitations would be sans-LabVIEW installation other then the troubleshooting head ache you get from developing applications without direct access to the hardware.
Thank you for your time and submissions.
-Nickerbocker

I am trying to get the "Shared Variable Client - Server" project example compiled so that both the server and client vi's can be run as executables on a standalone machine.
I have created 3 build specifications:
1. "My Server" which is the compiled EXE of the server.lvib. Added that entire library to the source.
2. "My Client" which is the compiled EXE of the client.lvib. Added that entire library to the source.
3. "My Installer" which is the installation package of the vi's and NI supporting software. In the additional installers I have added:
* NI DataSocket
* NI LabVIEW Run-Time Engine 8.2
* NI Measurement & Automation Explorer 4.1
* NI Variable Engine
* NI Variable Manager
* NI-DAQmx 8.3
Some of those are added for future needs. Installed the package on my target machine and run the server executable it appears to run fine but I get various error messages from my client.exe package (which I won't go into detail here, yet). Upon stopping the server I get the message "LabVIEW: (Hex 0x8BBB0005) Unable to locate variable in he Shared Variable Engine. Deployment of this variable may have failed."
I check the services running and see that the "National Instruments PSP Server Locator" and the "National Instruments Variable Engine" are both in the list and "Started." I open up the Variable Manager that has been installed on my target machine and manually add the "waveform" and the "command" variables under a process I call "server" and start the process. After that I start my server.exe that I have compiled from the server.lvib library. The process gives no error messages until the stop button is pressed, and then I receive the message "LabVIEW: (Hex 0x8BBB0011) The connection to the server was disconnected."
The compiled programs run fine on my development machine as well as the uncompiled VIs within the LabVIEW development enviornment. Something tells me that I simply do not have the Variable engine properly configured on my target machine. Also, the process and variables should automatically be populated under "Local System" in the Variable Manager, right? I do not need to add them manually, or do I?
Thanks for your input!
-Nickerbocker

Shared variable no longer updates

All,
I have an RT Systems 2011 and have been using shared variables between the RT and Host. Working for months. Then I renamed a shared variable and it no longer updates. When I try to look at the variable in the NI Distributed System Manager, it reports that it does not exist.
I changed the name back to what it was, it is seen by the System Manager but the current value is not displayed.
I did a remote debug into the RT code and the variable is being updated.
Any ideas\comments\etc would be appreciated?
Thanks

What hardware are you using as your real-time target? When you mentioned that you are using "RT Systems 2011", are you using LabVIEW 2011 and the Real-Time Module?
After you updated the shared variable, did you re-deploy it? I highly recommend reading through the “Deployment and Hosting” section of the DeveloperZone Tutorial linked below:
http://www.ni.com/white-paper/4679/en/#toc3
Regards,
Cameron F
Applications Engineer
National Instruments

Is it possible to use a Shared Variable within a Chart?

I have a shared variable between a container report and a subreport called {@ResponseCount}:
whileprintingrecords;
shared numbervar Responses:= DistinctCount ({Survey_Response.RecipID})
I placed the variable in the report footer and the value is passing correctly. I would like to use this shared value in a chart; however, it is not even listed in the Chart Expert as an available field. I was placing the chart in Report Footer b.
I have also tried moving the variable value to the Report Header and placing the chart in the Report Footer, with the same result.
I tried changing the variable to a global variable, thinking that I was using the incorrect scope, but that passed a zero value instead.
Any suggestions would be welcome. Thank you.

Thank you for the response. Though I almost gave up on this, I did find a way to access the shared variable after all. I created a formula that simply called the variable formula. For this example, I was using a shared variable to pull a value from my container report into my sub report for use in a chart.
In my container report I created the shared variable {@Get_Responses}:
whileprintingrecords;
shared numbervar Responses:= DistinctCount ({Survey_Response.RecipID})
In my sub report I created the formula to call the above variable {@Fetch_Responses}
whileprintingrecords;
shared numbervar Responses;
Then, again in my sub report, I created a second formula to call the above formula {@ResponsesForChart}
{@Fetch_Responses}
This last formula was then available for use in the chart I needed to create.

Inconsistent Network Shared Variables

I will eventually be implementing a controls program on a machine using cfp. Before the cfp gets here, I am getting practice in network shared variables by trying to pass shared variables between two VIs on my computer. I have attached the two VIs and a screen shot of my project. I run a queued state machine and after the initialization routine is done, I run the control portion of the program. The control program is titled 'The4Mprocedure2.vi' and the QSM is titled '4M_QueueDrivenStateMachine'. In the initialization routine of the QSM, 'FALSE' is written to the boolean network shared variable, 'Run_4M_Procedure'. After the initialization routine is done, and a set of certain parameters are met, the QSM writes the value 'TRUE' to 'Run_4M_Procedure'. Ideally, The4Mprocedure2.vi would read the shared variable, and when the value is 'TRUE' The4Mprocedure2.vi would run. The4Mprocedure2.vi has a case statement that causes to run the program when 'Run_4M_Procedure' = TRUE. The4Mprocedure2.vi does not run when the variable is FALSE.
The problem that I am having is that The4Mprocedure2.vi does not always recognize that the value of my shared variable has changed. When the QSM passes the value of 'TRUE' to the controls program, The4Mprocedure2.vi will sometimes still read the network shared variable as FALSE. Sometimes, I have to restart the controls program several times while the QSM is running to ensure that 'TRUE' is passed to the controls portion. Why does my controls program not recognize when the network shared variable changes values?
Message Edited by tquintana55 on 07-14-2008 11:04 AM
Attachments:
The4MProcedure21.vi ‏87 KB
ProjectScreenShot1.JPG ‏68 KB
4M_QueueDrivenStateMachine1.vi ‏131 KB

Hi tquintana55,
I believe your Issue is related to the methods that LabVIEW subscribes to the shared variables. Here is a link to a related article:
How to Avoid the "0" Value at First Read of a Shared Variable in LabVIEW 8.5.x?
To resolve this you can move your Run_4M_Procedure inside the while loop.
Sappster

Sharing variables between apps

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