Go to very beginning of UINavigationController after going some pages deep

I want to go to the very beginning 开发者_JAVA百科of the UINavigationController after going deep several pages. If I try the following code, it will only go back one view.

[self.navigationController popViewControllerAnimated:YES];

I want to do this action on a "cancel" button placed on the top right.

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[self.navigationController popToRootViewControllerAnimated:YES];