Opening multiple copies of application

You really should try to go with plan B imo. Perhaps you could share some of the issues you're having with implementing the document-based application architecture and some of us could help you out. I'm certainly no expert, but one of the things I've learned is that you should really avoid fighting/circumventing Apple's design patterns and go with the way they want you to do it at all costs.

 

I would go with plan B, however, if you really want to have multiple instances of the same application you should be able to do it using QProcess. So, when you receive a new 'file open' signal, you can create and start a new QProcess object. I'm not certain, but I'm pretty sure you can use QProcess to start another instance of the same application.

I still think plan B is the right thing to do. Opening multiple instances of your program just seems like a hack or a (no offense intended) lazy way out.

 

I don't know Mac programming, so this may or may not be doable.

I think you could look into using two programs. The first program is the clickable one (and can be associated with the file type). So it loads and has the file name/path. Then it needs to start second program giving the file as a parameter. Presumably, starting the second programming will use a different mechanism that won't be intercepted by the OS. I'm thinking something like fork or exec, but that might not change the name associated with the process. Anyway, you would want the first program to exit, so then the OS will not think there is an instance of it already running. You would have multiple instances of the second program running.

 

When the user opens a document intended for your application, and your application is already running, then the Finder will send a message to your application to open that document. When you receive that message, you should check whether there is already an open document. If not, open the document. If yes, you can call the OS to open a copy of your application, and pass the document to it.

 

There is a hack way to do it, but I wouldn't recommend it

You can launch multiple copies of applications issuing the following command:
/Applications/(your app name).app/Contents/MacOS/(yourappname)

For example, if you wanted to launch multiple instances of Safari, issue the following command in Terminal:
/Applications/Safari.app/Contents/MacOS/Safari

This doesn't apply to Java applications and other non-cocoa/carbon apps, so be careful, but it is possible.

Essentially what you could do is create a second app that basically takes the opened file, then calls your app using the above method and provides the file name as an argument.

Again, its a hack and there are 0 guarantees of how the operating system will treat multiple instances of your app.....

 

I'm glad you got it figured out. I never tried doing that myself but it's good to know. You're right about the plan B approach. No sense making it more complicated than it needs to be, especially considering it's only going to be used by a few users.