在iOS上使用ARC将CALayer的内容设置为CGImageRef [英] Setting the contents of a CALayer to a CGImageRef on iOS with ARC on

问题描述

以下代码使用手动内存管理进行编译，但在ARC下失败：

The following code compiles fine with manual memory management, but fails under ARC:

CALayer *layer = [CALayer layer];
layer.contents = [[UIImage imageNamed:@"dial.png"] CGImage];

错误是：

自动引用计数问题：使用ARC

Automatic Reference Counting Issue: Implicit conversion of a non-Objective-C pointer type 'CGImageRef' (aka 'struct CGImage *') to 'id' is disallowed with ARC

如何使用ARC运行

推荐答案

CoreFoundation对象不由ARC管理。 ARC只适用于Objective-C对象，并且不会隐式地知道当从（或到）非对象指针类型转换时转移所有权。

CoreFoundation objets aren't managed by ARC. ARC only works with Objective-C objets and does not implicitly know how to transfer the ownership when casting from (or to) an non-object pointer type.

告诉ARC如何在转换期间传递对象的所有权：

You need to tell ARC how the ownership of the objet is transferred during the cast:

layer.contents = (__bridge id) [[UIImage imageNamed:@"dial.png"] CGImage];

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