Freezing and thawing threads in Xcode

How do I freeze and thaw threads in Xcode like I can in Visual Studio? Th开发者_如何学JAVAanks.

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To suspend a thread in your running application . . .

• Pause your application’s execution, or wait for it to hit a breakpoint.
• In the Debug Navigator, Control-click the desired thread.
• In the contextual menu that appears, select Suspend Thread.

http://developer.apple.com/library/mac/#documentation/ToolsLanguages/Conceptual/Xcode4UserGuide/Debugging/Debugging.html