iOS开发：如何在将视图控制器推入导航堆栈之前预先加载视图控制器？

I'm diving into iOS development and I'm building a puzzle game to help me become familiar with the platform. I have AdWhirl displaying ads in the score screen that is displayed when the user completes a puzzle. The problem is, it takes at least a few seconds for the score screen view controller to request and receive the ad, in which time the user looks at the score and moves onto a different view. I'm planning to implement an animation that occurs when the user solves a puzzle and the time it takes for the animation to finish would be a good time to request and receive the ad that will be displayed in the next (score) view the user will be taken too.I'm diving into iOS development and I'm buildin