Is it possible to copy iPhone data to Mac using Xcode? I connected my iphone to a my friend Mac which running Xcode to debug an app. After plugging, I clicked "Trust [this computer]" and it took some time to detect the device in Xcode. While debugging, he opened a window which I saw my photos on my device and he switched back again to debug window. 

After fixing the app bug, I asked him to un-sync my device and he told me your data is just synced with itunes and when you unplug your device, I cannot see your data (photos) any more.

Actually, I am not convinced and I am thinking wherther he copied my iPhone data including my photos to his computer or not. I am sure he did not use iTunes during this process. 

Can anybody tell me it is possible to copy iPhone data to Mac during Xcode debugging?
The window that popped up was probably the Photos app, that will typically auto start when a new device with photos is attached. Your friend did the right thing by closing it when he saw it happen. No copies of your photos would have been made at this time, only thumbnails were downloaded and those would be removed when Photos was closed.

He theoretically could have copied some data, but Xcode will not automatically copy anything sensitive, so unless he is a really sneaky 'friend' that set up his Mac to copy in the background in advance, I think you are probably OK.