swift - EKEvent的镜像不显示数据

Question

对于我的 EVReflection库 我遇到了一个 EKEvent 的镜像没有返回任何信息的情况。即使在完成基础知识时，Mirror 也没有返回任何东西。当您在 Mirror 行之后设置断点时，您会看到 Mirror 对象中没有任何内容。这是错误还是我遗漏了什么？

更新: 我扩展了使用旧的 Objective C objc_property_t 和 property_getName 函数获取属性的演示。它将返回一个属性列表。但是当你得到 .value(forKey:

#if os(tvOS)
    // Eventkit is not supported on tvOS
#else


import XCTest
import Foundation
import EventKit


let store = EKEventStore()

class EVReflectionEventKitTests: XCTestCase {
    func testEventKit() {

        let exp = expectation(description: "eventStore")

        store.requestAccess(to: .event, completion: { (granted, error) in
            let event = EKEvent(eventStore: store)
            event.startDate = Date().addingTimeInterval(10000)
            event.title = "title"
            event.location = "here"
            event.endDate = Date().addingTimeInterval(20000)
            event.notes = "notes"

            event.calendar = store.defaultCalendarForNewEvents
            event.addAlarm(EKAlarm(absoluteDate: Date().addingTimeInterval(10000)))

            //WARNING: You will get events in your agenda! Disable next line if you don't want that
            //try? store.save(event, span: EKSpan.thisEvent, commit: true)

            let m = Mirror(reflecting: event)
            print("mirror children = \(m.children.count)")

            let oc = self.properties(event)
            print(oc)

            for p in oc {
                var value: Any? = nil
                value = event.value(forKey: p)
                print("\(p) = \(String(describing: value))")
            }

            exp.fulfill()
        })

        waitForExpectations(timeout: 10) { error in
            XCTAssertNil(error, "\(error?.localizedDescription ?? "")")
        }
    }

    func properties(_ classToInspect: NSObject) -> [String] {
        var count = UInt32()
        let classToInspect = NSURL.self
        let properties = class_copyPropertyList(classToInspect, &count)
        var propertyNames = [String]()
        let intCount = Int(count)
        for i in 0 ..< intCount {
            let property : objc_property_t = properties![i]!
            guard let propertyName = NSString(utf8String: property_getName(property)) as String? else {
                debugPrint("Couldn't unwrap property name for \(property)")
                break
            }
            propertyNames.append(propertyName)
        }

        free(properties)
        return propertyNames
    }
}

#endif

Answer 1

这似乎是有意为之的行为:

• _ObjCMirror child count implementation只是遵从 _getObjCCount shim，它的实际函数名称是 specified作为 swift_ObjCMirror_count。
• swift_ObjCMirror_count当 REFLECT_OBJC_IVARS 被定义为错误值时，被设置为始终返回 0。
• 猜猜 Swift 源代码中 REFLECT_OBJC_IVARS 的值是多少？没错，就是set to 0.

如果它不为零，它会转储 ivars，而不是属性。属性的 getter 属性可以做到这一点，因此没有与属性名称匹配的方法，并且它的支持 ivar 也可以与属性命名不同，如果有的话:这两者都可能导致 -valueForKey:失败。大多数类不会禁用通过键值编码直接访问 ivar，因此您可能想尝试转储 ivar 并访问它们。

您可能还想注意到一些类在其布局方面存在缺陷，例如 NSURL，was explicitly blacklisted from reflection即使为 Obj-C 类启用了反射!

预计到达时间:这是一个转储 ivar 的示例。不幸的是，它在这种情况下并不是很有用。

根据ivars生成字典的代码:

func makeDictionary(describing object: AnyObject) -> Dictionary<String, Any> {
    var dict = [String: Any]()
    guard let cls = object_getClass(object) else {
        print("object has no class:", object)
        return dict
    }

    var ivarCount: UInt32 = 0
    guard let ivarsPtr: UnsafeMutablePointer<Ivar?> = class_copyIvarList(cls, &ivarCount), ivarCount > 0
    else {
        print("object has no ivars, or failed to get any:", object)
        return dict
    }

    let ivars = UnsafeBufferPointer(start: ivarsPtr, count: numericCast(ivarCount))
    for ivar in ivars {
        guard let int8Ptr = ivar_getName(ivar) else {
            print("failed to get name for ivar:", ivar as Any)
            continue
        }

        let name = String(cString: int8Ptr)
        let value = object_getIvar(object, ivar)
        print("value for \(name):", value as Any)
        dict[name] = value ?? object.value(forKey: name) ?? NSNull()
    }
    return dict
}

以及按照您的问题中所述创建的事件的输出(手动硬包装以便于查看):

dictionary version based on direct ivar access: 
["isYearlessLeapMonthBirthday": 0
, "_birthdayPersonID": 0
, "_sliceDate": <null>
, "nameForBirthday": <null>
, "_futureLocalUidForSliceChild": <null>
, "isYearlessBirthday": 0
, "_cachedDuration": <null>
, "_cachedStartOfDayForStartDate": <null>
, "_isPhantom": 0
, "lunarCalendarString": <null>
, "_cachedIsMultiDayTimedEvent": <null>
, "_cachedTimeValuesCalendar": <null>
, "birthdayTitle": <null>
, "_cachedStartOfDayForEndDate": <null>
, "_cachedDaysSpanned": <null>
, "_cachedJunkStatus": 0
, "sliceParentID": <null>
, "participantsStatus": 0
]