I had this problem until I put the Xcode 6-beta application file from inside a folder I had in my application directory to the Application directory itself. Restarted computer. Then it worked.
To test, I created a folder in my Application directory again and put my Xcode application in there and, again, it did not work. Put it back into Application directory itself; it worked. I didn't even have to restart in these cases.
I would really hope Apple is beyond hardcoding paths.
After I found some solutions on the web, a combination of procedures worked for me:
Close Xcode and iOS Simulator (and all related applications)
Install (or reinstall) Xcode6-Beta to Applications folder (direct from the .dmg file)
Open Xcode6-Beta and go to Xcode -> Preferences -> Locations -> Command Line Tools and select "Xcode 6.0" (be sure that you've selected the one in Applications folder)
Launch the iOS Simulator and go to iOS Simulator -> Reset Content and Settings...
Close all the applications and restart your mac (I unchecked "Reopen windows...")
I got this problem after renaming the default folder name "Xcode-Beta2" to "Xcode". When I renamed it back to "Xcode-Beta2", the simulator worked as before.
I'm using Xcode 6 beta 2 and has problem (error code = 4 in my case) running iPad simulators. I think I had the issue because I'm running dual Mac OS boot and the Xcode is launched from another startup disk
I did both steps recommended by @ayalcinkaya and @apascual, and this worked for me.
Change the "Command Line Tool" to Xcode BETA2 (from 5.1.1 in my case) in "Xcode->Preference->Locations"
Open Xcode 6 beta 2
Go to the menu Xcode > Open Developer Tool > iOS Simulator
Even if an error dialog shows up, you still would have access to the iOS Simulator's menu
Select Hardware > Devices, and switch between iPad devices and this apparently made the simulators reconfigured
While the simulator is running, run the app with the selected simulator.
After going through this manual process once, everything is fine.
i was facing the same problem, what i done is I downloaded simulator for IOS7
what you need to do is go to:-
1.Xcode->preferences->Downloads->Components
2.after that in your project under general settings-select Deployment target as 7.0
3.the last thing is select any simulator under 7.0 :)
I received this error trying to run one of my iPad only apps on the iPhone Simulator. It's built as a universal app, I've run it multiple times on the iPhone for testing, and I only recently checked the "iPad" only checkbox in the Target config.
When trying to run it on my iPhone Device, I got the much more helpful error message: "The application at [/location/..../Name.app] can only be installed on iPads."
The most common cause for the error reporting is that DYLD_INSERT_LIBRARIES is set. Most people reporting this issue have had it set in /etc/launchd.conf. You can edit that file to remove it (or just delete the file as that's likely the only line) and reboot to address the issue.
Another possible cause for this problem is that you may have renamed Xcode.app after running it the first time. If that's the case, just reboot (or rename it back to what it was before).
I also had this problem and found the solution by doing following steps:
Initially I downloaded Xcode 6 library in Documentation section under the path Xcode --> Preferences --> Downloads and restart my xcode but didn't solve my problem.
After that ->
Downloaded and installed the iOS 7.1 Simulator under the path Xcode --> Preferences --> Downloads.
Restart xcode again and the problem solved.
I am facing same issue again next morning.
Unsetting the DYLD_INSERT_LIBRARIES variable solves my problem:
a) Open terminal and type "sudo vi /etc/launchd.conf" command and press Enter
b) Press I "Insert" mode and change this
c) Save changes by typing ":wq" Press Enter
d) Reboot your system and problem solved.
Prior to that I didn't found any iOS version in front of each listed devices
but after installation or by unsetting DYLD_INSERT_LIBRARIES variable I found the same in front of each devices.
But for me, before step 5, I have deleted the simulator device (select and by pressing Delete key from keyboard) Which device is giving the Problem.
Reference: apascual answer
What worked for me is just open the simulator and leave it open for a while it will probably boot up. I think in my case it was just trying to load the things or something like that or just my mac is slow.
Try leaving the simulator open for some time if it still does not boot then you may try any of the solutions here.