ios - 在 Swift 中按名称获取实例变量

Question

我正在尝试快速复制此功能:https://stackoverflow.com/a/11774276/4102858 .我能够在 Swift 中成功地重新创建 allPropertyNames() 。但是，我在使用方法 pointerOfIvarForPropertyNamed() 执行相同操作时遇到了问题。主要原因是 Objc 解决方案使用了函数 object_getInstanceVariable()，它在 Swift 中不可用。

TLDL:我正在尝试在 Swift 中重新创建此方法:

- (void *)pointerOfIvarForPropertyNamed:(NSString *)name
{
    objc_property_t property = class_getProperty([self class], [name UTF8String]);
    const char *attr = property_getAttributes(property);
    const char *ivarName = strchr(attr, 'V') + 1;
    Ivar ivar = object_getInstanceVariable(self, ivarName, NULL);
    return (char *)self + ivar_getOffset(ivar);
}

这是我现在所在的位置:

func pointerOfIvarForPropertyNamed(name: String) -> AnyObject {

    func unicodeValueOfString(string: String) -> UInt32 {
        for s in String(string).unicodeScalars {
            return s.value
        }
        return 0
    }

    var property: COpaquePointer = class_getProperty(self.classForCoder, (name as NSString).UTF8String)
    var attr: UnsafePointer<Int8> = property_getAttributes(property)
    var ivarName: UnsafeMutablePointer<Int8> = strchr(attributesPointer, Int32(unicodeValueOfString("V"))) + 1

    //object_getInstanceVariable() not available in Swift

}

问题:

函数 object_getInstanceVariable() 在 Swift 中不可用

我普遍缺乏使用 Objective-C 运行时的经验

Answer 1

来自 Swift 文档(强调我的):

If you have experience with Objective-C, you may know that it provides two ways to store values and references as part of a class instance. In addition to properties, you can use instance variables as a backing store for the values stored in a property.

Swift unifies these concepts into a single property declaration. A Swift property does not have a corresponding instance variable, and the backing store for a property is not accessed directly. This approach avoids confusion about how the value is accessed in different contexts and simplifies the property’s declaration into a single, definitive statement. All information about the property—including its name, type, and memory management characteristics—is defined in a single location as part of the type’s definition.

根据 pointerOfIvarForPropertyNamed 的使用方式，您可能无法将该方法直接翻译成 Swift，因为它没有 Ivars。您可以 use Key-Value Coding实现你想要的。

如果你想扩展这个方法的使用方法，我可以适当扩展我的答案。