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特定于设备的加载类别

发布于 2024-12-07 17:17:54 字数 144 浏览 1 评论 0原文

我有一个 iPhone 应用程序，我想使其通用，大多数视图可以保持不变，但需要针对 iPad 进行一些小的修改。

是否可以根据用户使用的设备加载类别？

或者有更好的方法吗？通用方法（而不是每次创建类的新实例时专门检查，并在两个类之间进行选择）

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甩你一脸翔 2024-12-14 17:17:54

您可以在运行时通过一些方法混合来做到这一点。举一个简单的例子，如果您想在 UIView 子类中拥有一个与设备相关的 drawRect: 方法，您可以编写两个方法，并决定在该类被调用时使用哪个方法。已初始化：

#import <objc/runtime.h>

+ (void)initialize
{
    Class c = self;
    SEL originalSelector = @selector(drawRect:);
    SEL newSelector = (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) 
                      ? @selector(drawRect_iPad:) 
                      : @selector(drawRect_iPhone:);
    Method origMethod = class_getInstanceMethod(c, originalSelector);
    Method newMethod = class_getInstanceMethod(c, newSelector);
    if (class_addMethod(c, originalSelector, method_getImplementation(newMethod), method_getTypeEncoding(newMethod))) {
        class_replaceMethod(c, newSelector, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
    } else {
        method_exchangeImplementations(origMethod, newMethod);
    }
}

- (void)drawRect_iPhone:(CGRect)rect
{
    [[UIColor greenColor] set];
    UIRectFill(self.bounds);
}

- (void)drawRect_iPad:(CGRect)rect
{
    [[UIColor redColor] set];
    UIRectFill(self.bounds);
}

- (void)drawRect:(CGRect)rect
{
    //won't be used
}

这会导致 iPad 上显示红色视图，iPhone 上显示绿色视图。

You could do this with some method swizzling at runtime. As a simple example, if you want to have a device-dependent drawRect: method in your UIView subclass, you could write two methods and decide which to use when the class is initialized:

#import <objc/runtime.h>

+ (void)initialize
{
    Class c = self;
    SEL originalSelector = @selector(drawRect:);
    SEL newSelector = (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) 
                      ? @selector(drawRect_iPad:) 
                      : @selector(drawRect_iPhone:);
    Method origMethod = class_getInstanceMethod(c, originalSelector);
    Method newMethod = class_getInstanceMethod(c, newSelector);
    if (class_addMethod(c, originalSelector, method_getImplementation(newMethod), method_getTypeEncoding(newMethod))) {
        class_replaceMethod(c, newSelector, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
    } else {
        method_exchangeImplementations(origMethod, newMethod);
    }
}

- (void)drawRect_iPhone:(CGRect)rect
{
    [[UIColor greenColor] set];
    UIRectFill(self.bounds);
}

- (void)drawRect_iPad:(CGRect)rect
{
    [[UIColor redColor] set];
    UIRectFill(self.bounds);
}

- (void)drawRect:(CGRect)rect
{
    //won't be used
}

This should result in a red view on the iPad and a green view on the iPhone.

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