最近遇到一個自定義類Tabbar的視圖，于是用模態(tài)方式去自由切換viewController，關(guān)鍵方法是：

- (void)transitionFromViewController:(UIViewController *)fromViewController toViewController:(UIViewController *)toViewController duration:(NSTimeInterval)duration options:(UIViewAnimationOptions)options animations:(void (^ __nullable)(void))animations completion:(void (^ __nullable)(BOOL finished))completion NS_AVAILABLE_IOS(5_0);

不過在完成之后 來回快速點擊會發(fā)現(xiàn)崩潰的問題
Unbalanced calls to begin/end appearance transitions for xxx
發(fā)現(xiàn) transitionFromViewController 這個方法若當(dāng)前viewController已在最前，就不應(yīng)該在調(diào)用該方法，于是解決辦法如下：

- (void)replaceFromViewController:(ALYBaseViewController *)first toViewController:(ALYBaseViewController *)second index:(NSInteger)idx completion:(void (^)(ALYBaseViewController *, ALYBaseViewController *, NSInteger))completion{
    // 判斷是否是一個vc
    if ([second isEqual:first] return;
    
    [self addChildViewController:second];
    [self transitionFromViewController:first toViewController:second duration:0 options:UIViewAnimationOptionTransitionNone animations:^{
        [second didMoveToParentViewController:self];
        [first willMoveToParentViewController:nil];
        [first removeFromParentViewController];

        completion(first, second, idx);
    } completion:^(BOOL finished) {
        if (finished) {
        }
    }];
}

記錄一下。