swift - 将项目转换为 Swift 4 时模糊使用 'filter'

Question

今天我尝试将我的项目转换为 Swift 4。我在这一行有错误:

return Forum.threads?.filter({ //... })

错误说:

Ambiguous use of 'filter'

Found this candidate (Swift.Set)

Found this candidate (Swift.Sequence)

threads对象在Forum中是这样实现的:

var threads: Set<Thread>?

那么如何解决这个..？感谢您的帮助

编辑:当在日志中显示错误时，以下是候选人:

Swift.Set:369:17: note: found this candidate
    public func filter(_ isIncluded: (Set.Element) throws -> Bool) rethrows -> Set<Element>
                ^
Swift.Sequence:35:17: note: found this candidate
    public func filter(_ isIncluded: (Self.Element) throws -> Bool) rethrows -> [Self.Element]

Answer 1

要解决这个问题，请在返回变量之前声明变量的类型。

let x: [Character] = input.filter{/**/}
return x

这消除了 filter{} 方法的返回类型的歧义。