如何消除具有相同名称的类型和模块的歧义? [英] How can I disambiguate a type and a module with the same name?

问题描述

我正在尝试在项目中使用KárolyLőrentey的基于B树的OrderedSet .但是，我遇到了一个问题，即我无法声明不合格的OrderedSet<T>，因为该名称在Foundation的NSOrderedSet(在Swift 3中作为OrderedSet导入)和BTree的OrderedSet之间冲突./p>

I'm trying to use Károly Lőrentey's B-tree based OrderedSet in a project. However, I'm running into an issue where I can't declare an unqualified OrderedSet<T> because the name conflicts between Foundation's NSOrderedSet (imported as OrderedSet in Swift 3) and BTree's OrderedSet.

let set = OrderedSet<Int>()
// error: 'OrderedSet' is ambiguous for type lookup in this context
// Found this candidate: Foundation.OrderedSet:3:14
// Found this candidate: BTree.OrderedSet:12:15

要解决此冲突，通常需要限定名称，然后再赋予BTree.OrderedSet<T>.但是，BTree模块还包含一个名为BTree的类.如果我写BTree.OrderedSet，Swift认为我指的是嵌套在BTree.BTree类型中的名为OrderedSet的类型.

To resolve this conflict, you would normally qualify the name, and that would give you BTree.OrderedSet<T>. However, the BTree module also contains a class named BTree. If I write BTree.OrderedSet, Swift thinks that I'm referring to a type named OrderedSet that is nested in the BTree.BTree type.

let set = BTree.OrderedSet<Int>()
// error: reference to generic type 'BTree' requires arguments in <...>

如果我不使用import BTree，则根本无法使用BTree名称.

If I don't import BTree, I can't use the BTree name at all.

// no import BTree
let set = BTree.OrderedSet<Int>()
// error: use of undeclared type 'BTree'

如何解决BTree类型和BTree模块之间的这种歧义?

How can I resolve this ambiguity between the BTree type and the BTree module?

推荐答案

可以使用鲜为人知的import (class|struct|func|protocol|enum) Module.Symbol语法消除类型的歧义.

The type can be disambiguated using the little-known import (class|struct|func|protocol|enum) Module.Symbol syntax.

import struct BTree.OrderedSet

从这一点开始，OrderedSet明确引用了BTree中的那个.

From this point on, OrderedSet unambiguously refers to the one in BTree.

如果在某些文件中这仍然是模棱两可或次优的，则可以创建一个Swift文件来使用类型别名重命名导入:

If this would still be ambiguous or sub-optimal in some files, you can create a Swift file to rename imports using typealiases:

// a.swift
import struct BTree.OrderedSet
typealias BTreeOrderedSet<T> = BTree.OrderedSet<T>

// b.swift
let foo = OrderedSet<Int>() // from Foundation
let bar = BTreeOrderedSet<Int>() // from BTree

Swift 3讨论了一种新语法，但失败了.

There was a new syntax discussed for Swift 3, but it fell through.

这篇关于如何消除具有相同名称的类型和模块的歧义?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！