Contrainer View - storyboard 的 a

Contrainer View storyboard 能拖出来的控件，继承UIView，当又与UIStackView 不一样，很奇葩的东西。

注1：可以直接拖入某个ViewController，并且可以多个！每一个对应连接了一个VC，相当于add childViewController了！
注2：链接有segue，但是不能直接用会崩溃，也不知道该怎么用才好。
注3：现在只能遍历自身的childViewControllers，然后去切换，感觉并没有纯代码方便啊，阿西吧。

// 找到对应的 childViewController（总觉得哪里不对！！！！）
- (void)checkChildViewController {
    [self.childViewControllers enumerateObjectsUsingBlock:^(__kindof UIViewController * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        
        if ([obj isKindOfClass:[AViewController class]]) {
            self.avc = obj;
        }
        else if ([obj isKindOfClass:[BViewController class]]) {
            self.bvc = obj;
        }
        else if ([obj isKindOfClass:[CViewController class]]) {
            self.cvc = obj;
            self.currendViewController = obj;// 最后一个拖进去的 container View 是当前的
        }
        else {
            // if  more vc
        }
    }];
}

// 切换
- (void)transitionToViewController:(UIViewController *)destinationViewController {
    if (destinationViewController == self.currendViewController) {
        return;
    }
    [self transitionFromViewController:self.currendViewController toViewController:destinationViewController duration:CGFLOAT_MIN options:UIViewAnimationOptionCurveEaseOut animations:^{
        
    } completion:^(BOOL finished) {
        
        self.currendViewController = destinationViewController;
    }];
}

顺便贴个纯代码的

    self.viewControllers = @[self.detailViewController,
                             self.performanceViewController,
                             self.relatedDocumentViewController,
                             self.similarProductViewController,
                             self.productAboutViewController];    

- (void)addChildViewControllers {
    
    int temp = 0;
    for (UIViewController *viewController in self.viewControllers) {
        [self addChildViewController:viewController];
        [viewController didMoveToParentViewController:self];
        viewController.view.frame = self.contentView.bounds;
        
        if (temp == 0) {
            [self.contentView addSubview:viewController.view];
            self.currentViewController = viewController;
        }
        temp ++;
    }
}

- (void)transitionViewControlleToIndex:(NSInteger)index {
    
    if (index >= self.viewControllers.count) {
        return ;
    }
    
    UIViewController *transitionedController = self.viewControllers[index];
    if (transitionedController != self.currentViewController) {
        
        [self transitionFromViewController:self.currentViewController
                          toViewController:transitionedController
                                  duration:CGFLOAT_MIN
                                   options:UIViewAnimationOptionCurveEaseInOut
                                animations:^{
                                    //
                                } completion:^(BOOL finished) {
                                    self.currentViewController = transitionedController;
                                }];
    }
}

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