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太多样板代码的开关语句 - iOS

ioscocoa-touchswitch-statementuilabelboilerplate
4

我有一个switch语句，会适当地向11个UILabel添加文本。然而，现在它变得有点冗长了，而且有太多相同的代码副本。我该如何进一步改进它呢？也许我可以创建一个标签数组，然后通过for循环来访问它们？

这里是switch语句的代码：

switch ([number_sorted count]) {

            case 1:
                label_1.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[0] integerValue]];
                break;

            case 2:
                label_1.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[0] integerValue]];
                label_2.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[1] integerValue]];
                break;

            case 3:
                label_1.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[0] integerValue]];
                label_2.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[1] integerValue]];
                label_3.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[2] integerValue]];
                break;

            case 4:
                label_1.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[0] integerValue]];
                label_2.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[1] integerValue]];
                label_3.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[2] integerValue]];
                label_4.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[3] integerValue]];
                break;

            case 5:
                label_1.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[0] integerValue]];
                label_2.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[1] integerValue]];
                label_3.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[2] integerValue]];
                label_4.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[3] integerValue]];
                label_5.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[4] integerValue]];
                break;

            case 6:
                label_1.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[0] integerValue]];
                label_2.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[1] integerValue]];
                label_3.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[2] integerValue]];
                label_4.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[3] integerValue]];
                label_5.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[4] integerValue]];
                label_6.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[5] integerValue]];
                break;

            case 7:
                label_1.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[0] integerValue]];
                label_2.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[1] integerValue]];
                label_3.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[2] integerValue]];
                label_4.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[3] integerValue]];
                label_5.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[4] integerValue]];
                label_6.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[5] integerValue]];
                label_7.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[6] integerValue]];
                break;

            case 8:
                label_1.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[0] integerValue]];
                label_2.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[1] integerValue]];
                label_3.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[2] integerValue]];
                label_4.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[3] integerValue]];
                label_5.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[4] integerValue]];
                label_6.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[5] integerValue]];
                label_7.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[6] integerValue]];
                label_8.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[7] integerValue]];
                break;

            case 9:
                label_1.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[0] integerValue]];
                label_2.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[1] integerValue]];
                label_3.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[2] integerValue]];
                label_4.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[3] integerValue]];
                label_5.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[4] integerValue]];
                label_6.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[5] integerValue]];
                label_7.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[6] integerValue]];
                label_8.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[7] integerValue]];
                label_9.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[8] integerValue]];
                break;

            case 10:
                label_1.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[0] integerValue]];
                label_2.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[1] integerValue]];
                label_3.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[2] integerValue]];
                label_4.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[3] integerValue]];
                label_5.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[4] integerValue]];
                label_6.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[5] integerValue]];
                label_7.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[6] integerValue]];
                label_8.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[7] integerValue]];
                label_9.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[8] integerValue]];
                label_10.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[9] integerValue]];
                break;

            case 11:
                label_1.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[0] integerValue]];
                label_2.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[1] integerValue]];
                label_3.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[2] integerValue]];
                label_4.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[3] integerValue]];
                label_5.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[4] integerValue]];
                label_6.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[5] integerValue]];
                label_7.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[6] integerValue]];
                label_8.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[7] integerValue]];
                label_9.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[8] integerValue]];
                label_10.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[9] integerValue]];
                label_11.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[10] integerValue]];
                break;

            default:
                break;
        }

感谢您抽出时间，丹。
不要使用11个ivars来存储标签，而是使用一个标签数组。这样代码就可以变成一个简单的循环。 - rmaddy
另一个解决方案是使用 objc_... 运行时函数动态查找标签，例如创建标签的选择器名称，然后调用 objc_msgSend()。这样就无需更改它们的声明。 - Thomas Tempelmann
3个回答
4
另一个选项是使用 switch 语句的 "fall through" 属性。
switch ([number_sorted count]) {
    case 11:
        label_11.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[10] integerValue]];
    case 10:
        label_10.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[9] integerValue]];
    case 9:
        label_9.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[8] integerValue]];
    case 8:
        label_8.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[7] integerValue]];
    case 7:
        label_7.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[6] integerValue]];
    case 6:
        label_6.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[5] integerValue]];
    case 5:
        label_5.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[4] integerValue]];
    case 4:
        label_4.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[3] integerValue]];
    case 3:
        label_3.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[2] integerValue]];
    case 2:
        label_2.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[1] integerValue]];
    case 1:
        label_1.text = [NSString stringWithFormat:@"%ld", (long)[number_sorted[0] integerValue]];
    default:
        break;
}
这个方法安全吗？因为（显而易见的原因）你已经省略了break语句。希望这不会导致任何意外的异常？ - Supertecnoboff
2
这个答案中的代码是安全的。通常情况下，如果缺少 break，那么这是一个错误，但在这种情况下，这正是你想要的。作为一种惯例，我总是在缺少 break 的位置添加注释，澄清它真的不应该存在。 - rmaddy
4
我还要补充一点，虽然这个答案看起来很好，但它仍然是错误的解决方案。它很脆弱，容易出现由于简单的拼写错误而导致的漏洞。它也不具备良好的可扩展性。你真的应该使用“循环”解决方案。它更少有漏洞，更具可扩展性，而且阅读和编写起来都更容易。 - rmaddy
我真的很不喜欢它。它仍然没有任何理由地重复了很多代码。这个概念很好，但在这种情况下，我会说它不合适。 - Daij-Djan
不幸的是，我必须同意DD和M的观点。这太糟糕了。编程的整个基本性质就是通过使用更高级别的概念来消除重复。虽然超级管理员能够理解在这种特定的编程语言中可以通过switch体进行跌落，但这是唯一的教育品质。这是OP提高集合、在代码中制作控件或其他方面的绝佳机会。（而且仍然没有人关心空白项！呵呵） - Fattie
显示剩余4条评论
2

使用两个数组：1. 包含所有标签，2. 包含各标签数量。
你已经有了第2部分，所以：

首先，在你的类中添加一个NSArray *_labels。
然后在viewDidLoad中执行_labels = @[label1, label2, label3];

然后针对开关操作进行处理。

for(int i = 0; i < number_sorted.count; i++) {
    ((UILabel*)_labels[i]).text = [NSString stringWithFormat:@"%ld", [number_sorted[i] integerValue]];
}
我收到了一个错误，类型为 id 的对象中未找到属性“text”。 - Supertecnoboff
1
@Daij-Djan，我在SO上看到很多变量和实例变量都有一个前导下划线“_”。我知道属性会生成带有前导下划线的实例变量，但为什么要以这种方式访问它们呢？通常，如果有属性，应该通过getter/setter（如self.labels）来访问值。是否存在不使用属性的偏见？是否有一些指导者/班级或教程推荐这样做？ - zaph
哦，我的错 @Supertecnoboff，请不要使用“.”语法或强制转换。我“修复”了代码。 - Daij-Djan
直接变量（direct vars）非常方便 :D - Daij-Djan
你甚至可以将它们放在.m文件中..在实现部分，即--> @implementation MyClass { id _myVar; } ... @end - Daij-Djan
显示剩余3条评论
2
只需将您的UILabel放入NSArray中，然后可以对该数组进行迭代。在Interface Builder中，您可以将一堆元素添加到IBOutletCollection中，这非常方便（只需将多个元素拖在一起，就像创建一个IBOutlet一样，它会提供创建IBOutletCollection的选项）。
请注意，IBOutletCollection不保证顺序。因此，您可能需要在IB中添加标记来跟踪它们。我经常在viewDidLoad中按标记对我的集合进行排序。
如果您以编程方式构建此系统，则可以直接将它们放入数组中。
有时候，跟踪标记仍然很麻烦，所以我会稍微作弊。我只使用subviews遍历所有视图并查找我的标签。然后，我按y-origin对它们进行排序并将它们放入数组中。当然，这有点脆弱，并且需要大量关于您的视图的特殊知识，但是视图控制器预计具有该知识。我偶尔使用这种技术创建混合的IB /编程界面，这样我就可以在IB中布置所有内容，但是在代码中连接所有内容（操作、字体选择等）。当存在许多几乎相同的UI元素时，我尤其这样做。
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