为什么不能快速对CKRecord对象使用下标？ [英] Why can't I use subscripting on a CKRecord object in swift?

问题描述

这困扰了我一段时间。我有理由为什么要在CKRecord上设置对象。

This has bothered me for a little while. Is there a reason why I need to do this to set an object on a CKRecord.

task.record?.setObject(task.reference, forKey:ReferenceField)

代替此

task.record?[ReferenceField] = task.reference 

从我在CKRecord文档中看到的内容来看，下标应该是友好的

From what I read in the docs CKRecord should be subscript friendly

推荐答案

该下标仅可从Objective-C获得，因为它是使用 objectForKeyedSubscript：和 setObject：forKeyedSubscript：实现的。幸运的是，扩展 CKRecord 以允许Swift下标很容易：

That subscripting is only available from Objective-C, since it's implemented using objectForKeyedSubscript: and setObject:forKeyedSubscript:. Happily, it's easy to extend CKRecord to allow Swift subscripting:

extension CKRecord {
    subscript(key: String) -> AnyObject! {
        get {
            return self.objectForKey(key)
        }
        set(newValue) {
            self.setObject(newValue as CKRecordValue, forKey: key)
        }
    }
}

NSHipster具有有关Objective-C下标的帖子，如果您想了解更多。我很惊讶Swift无法自动桥接。

NSHipster has a post on Objective-C subscripting if you want to know more. I'm surprised Swift doesn't bridge that automatically.

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