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动态设置UIVIEW控制器指针内联-C

casting uiviewcontroller cocoa-touch objective-c ios

Supertecnoboff · 技术社区 · 7 年前

我有一个带有for循环的iOS应用程序,它可以创建、设置和添加自定义视图控制器。问题是我需要动态地设置 UIViewController 对象设置为正确的类,具体取决于当前循环数。这是我的代码:

// Loop through the data and setup the switches.

for (NSUInteger loop = 0; loop < [switchLabels count]; loop++) {

    // Create the view controller object.
    UIViewController *screen;

    // Create the custom switch view.

    if (loop < 3) {
        screen = [[CustomSwitchView alloc] initWithNibName:@"CustomSwitchView" bundle:nil];
    } else {
        screen = [[CustomTripleSwitchView alloc] initWithNibName:@"CustomTripleSwitchView" bundle:nil];
    }

    // Create the custom switch view.
    [screen setPassedInType:switchTypes[loop]];
    [screen setDelegate:self];
    [self addChildViewController:screen];
    [screen.view setFrame:CGRectMake((self.view.frame.size.width - 150), ((UILabel *)switchLabels[loop]).frame.origin.y, 144, 72)];
    [scrollTopView addSubview:screen.view];
    [screen didMoveToParentViewController:self];
    [screen setTitles:switchTitles[loop] state:[switchSettings[loop] boolValue]];
}

问题是,上面的一些方法调用会出现错误:

“uiviewcontroller”的visible@interface没有声明选择器….

为了解决这个问题,我需要键入cast对象 screen . 但是,我需要根据for循环数动态地键入cast:

如果循环小于3,则需要将对象类型转换为 CustomSwitchView ,否则我需要键入cast CustomTripleSwitchView . 我该怎么做?例如,我尝试了下面的代码,但没有成功:

(loop < 3 ? (CustomSwitchView *) : (CustomTripleSwitchView *))

谢谢你的时间,丹。

1 回复 | 直到 7 年前

danh 7 年前

有几种方法可以处理这个问题。对现有代码的最小影响将是将方法区分为一般应用于UIViewControllers的方法和那些特别适用于子类的方法。调用被声明为特定子类的堆栈变量的子类方法…

for (NSUInteger loop = 0; loop < [switchLabels count]; loop++) {

    // Create the view controller object.
    UIViewController *vc;

    // Create the custom switch view.

    if (loop < 3) {
        CustomSwitchView *screen = [[CustomSwitchView alloc] initWithNibName:@"CustomSwitchView" bundle:nil];
        [screen setPassedInType:switchTypes[loop]];
        [screen setDelegate:self];
        [screen setTitles:switchTitles[loop] state:[switchSettings[loop] boolValue]];
        vc = screen;
    } else {
        CustomTripleSwitchView *screen = [[CustomTripleSwitchView alloc] initWithNibName:@"CustomTripleSwitchView" bundle:nil];
        [screen setPassedInType:switchTypes[loop]];
        [screen setDelegate:self];
        [screen setTitles:switchTitles[loop] state:[switchSettings[loop] boolValue]];
        vc = screen;
    }

    // Create the custom switch view.
    [self addChildViewController:vc];
    [vc.view setFrame:CGRectMake((self.view.frame.size.width - 150), ((UILabel *)switchLabels[loop]).frame.origin.y, 144, 72)];
    [scrollTopView addSubview:vc.view];
    [vc didMoveToParentViewController:self];
}

如果我们在项目中遇到这个问题,这是一个好的解决方案。当你看到这类事情激增时,是时候开始思考:(a)我应该在每个类上定义一个协议(作为一个适当的建议者),还是(b)这些真正的子类彼此相关,比如 CustomTripleSwitchView 真的是 CustomSwitchView 是吗?