问题
I am using Swift for an iOS app.
I need to store a DateComponents object as a field in CloudKit.
How would I do that?
So far I think I need to set the CloudKit field to type Bytes, and convert the DateComponents object to a Data object. Looking at the documentation for the Data class, I can't figure out how to initialize the Data object. I have no idea how to use the UnsafeBufferPointer used in one of the initializers.
The following code gives a runtime error:
newRecord.setObject((dateComponents as! __CKRecordObjCValue), forKey: DatabaseNameStrings.fieldTime)
Here's the runtime error message in the debug window:
Could not cast value of type 'NSDateComponents' (0x1d04208c8) to '__C.CKRecordValue' (0x1d0420ab0).
I also need to convert Data to DateComponents. Both Data and DateComponents classes conform to the Codable protocol, which inherits the Decoder protocol. One of DateComponents' initializers is:
init(from: Decoder)
which leads me to suspect there is a way to use that init to convert type Data to DateComponents after I get the Data object from the CloudKit field of type Bytes.
The following code:
if let data = privateRecord.object(forKey: DatabaseNameStrings.fieldTime) as? Data {
let dateComponents = DateComponents(from: data) // error here
}
generates an error in the Xcode editor which says:
Argument type 'Data' does not conform to expected type 'Decoder'
I thought since both Data and DateComponents conform to Decoder protocol that code would work.
回答1:
It seems you might be over-engineering this a bit. Here are a couple alternatives you could consider:
- Store the date in a date field on CloudKit and re-parse to date components in your app.
- Store each date component (year, month, day, etc.) as separate integer fields on CloudKit (or as strings if you want to pre-format them).
Just a thought. Good luck. :)
来源：https://stackoverflow.com/questions/56895587/how-would-i-save-an-object-of-type-datecomponents-to-a-cloudkit-field