无法推断Swift 3 NSCache通用参数'KeyType'

问题描述

此代码在Swift 2.x中有效:

This code worked in Swift 2.x:

/// An internal in-memory cache
private var dataCache = NSCache.init()

在 Swift 3 中会导致编译错误:

Generic parameter 'KeyType' could not be inferred

为什么会这样，我应该如何重构它(迁移工具未进行修改)?

Why is that so and how should I refactor this (Migration tool did not pick this up)?

推荐答案

• 在第一个Swift 3 beta中，NSCache已更改为Cache.
• 在最新的Beta(目前为5个)中，它已还原为NSCache.
• In the first Swift 3 betas NSCache has been changed to Cache.
• In the latest betas (currently 5) it has been reverted to NSCache.

无论如何，NSCache现在是通用名称.

Anyway NSCache is now a generic.

public class NSCache<KeyType : AnyObject, ObjectType : AnyObject> : NSObject { ...

所以最通用的语法是

private var dataCache = NSCache<AnyObject, AnyObject>()

不需要显式的init()(甚至在Swift 2中也不需要)

The explicit init() is not needed (not even in Swift 2)

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