是否可以通过函数传递类类型并尝试将类转换为给定的类类型?我尝试了以下代码。
class Section {}
class TimeSection: Section {}
class TaskSection: Section {}
let timeSection = TimeSection()
let taskSection = TaskSection()
let sections = [timeSection, taskSection]
func findSection(from classType: Section.Type) {
for section in sections {
guard let section = section as? classType else { continue }
print("Found section")
}
}
findSection(from: TimeSection.self)
但是我总是会收到此错误:
Use of undeclared type 'classType'
答案 0 :(得分:3)
您可以使用泛型函数并将type参数限制为Section。
import Foundation
class Section {}
class TimeSection: Section {}
class TaskSection: Section {}
class NoSection {}
let timeSection = TimeSection()
let taskSection = TaskSection()
let sections = [timeSection, taskSection]
func findSection<T: Section>(from classType: T.Type) {
for section in sections {
guard let section = section as? T else { continue }
print("Found section: \(section)")
}
}
findSection(from: TimeSection.self) // Found section: __lldb_expr_9.TimeSection
findSection(from: TaskSection.self) // Found section: __lldb_expr_9.TaskSection
findSection(from: NoSection.self) // won't compile
答案 1 :(得分:0)
classType
实际上不是一种类型。它是一个包含Section.Type
实例的参数。因此,您不能将其与as?
一起使用。
由于它是一个参数,因此可以将其与==
进行比较。 ==
的另一端应该是section
的元类型的实例,可以由type(of:)
获取。
func findSection(from classType: Section.Type) {
for section in sections {
if type(of: section) == classType {
print("Found section")
break
}
}
}