Record your iPhone or iPad output on your Mac
Before Yosemite, if you wanted to create a video of your iPhone or iPad screen, you needed additional hardware and software such as Elgato’s Game Capture HD. Now all you need is your iOS device’s USB cable.
Plug the cable into the Lightning port on your iPhone or iPad and then into a USB socket on your Mac. Launch QuickTime Player and choose New Movie Recording or New Audio Recording from the File menu. By default, QuickTime will take input from your Mac’s iSight camera, but you can change that by clicking the down arrow next to the record button and choosing your iPhone or iPad. Now when you press record, QuickTime will grab the audio and video output from your iOS device and record it. You can use it to make play-through videos of iOS games, video reviews of apps, or anything else you want to grab.
You don’t even need to record the output; you can use QuickTime as a way to ‘mirror’ output on your Mac, like a wired version of AirPlay mirroring. Expand the QuickTime window to full-screen and you can play iPad or iPhone games using your Mac’s display.