use of undeclared type 'Date' Xcode 9 Swift 4

问题

This is my code in xcode 9 playground

class Tutorial: Codable {
    let title: String
    let author: String
    let editor: String
    let type: String
    let publishDate: Date

    init(title: String, author: String, editor: String, type: String, publishDate: Date) {
        self.title = title
        self.author = author
        self.editor = editor
        self.type = type
        self.publishDate = publishDate
    }
}

its showing error use of undeclared type 'Date'

回答1:

The Date struct is part of the Foundation framework.

Add import Foundation at the beginning of your playground.

As a general rule, you should always import at least Foundation because many of the everyday types we use are part of Foundation. You can also import only UIKit (because UIKit automatically imports Foundation).

来源：https://stackoverflow.com/questions/44944220/use-of-undeclared-type-date-xcode-9-swift-4