冗余一致性错误消息 Swift 2

问题描述

我将我的项目更新到 Swift 2，并收到了一堆 XXX 与 YYY 协议的冗余一致性.当类符合 CustomStringConvertible 时，这种情况尤其经常(或总是)发生.还有一些带有 Equatable 的地方.

class GraphFeatureNumbersetRange: GraphFeature, CustomStringConvertible {//<--- 在此处获取错误...}

我怀疑在实现 var description: String { get } 或协议要求的任何方法时，我不需要明确遵守协议.我应该按照 fixit 说明删除所有这些吗?如果一个类实现了协议的所有方法，Swift 现在会自动推断一致性吗?

解决方案

如果子类声明一致性，您将在 Xcode 7 (Swift 2) 中收到该错误消息到一个已经从超类继承的协议.示例:

class MyClass : CustomStringConvertible {变量描述:字符串{返回MyClass"}}类子类:MyClass，CustomStringConvertible {覆盖变量描述:字符串{返回子类"}}

错误日志显示:

main.swift:10:27: 错误:子类"与协议CustomStringConvertible"的冗余一致性类子类:MyClass，CustomStringConvertible {^main.swift:10:7: 注意:子类"从这里的超类继承了对协议CustomStringConvertible"的一致性类子类:MyClass，CustomStringConvertible {^

从子类声明中删除协议一致性解决问题:

class 子类:MyClass {覆盖变量描述:字符串{返回子类"}}

但是超类必须显式声明一致性，它是不会从 description 的存在自动推断财产.

I updated my project to Swift 2, and received a bunch of redundant conformance of XXX to protocol YYY. This happens especially often (or always) when a class conforms to CustomStringConvertible. Also some place with Equatable.

class GraphFeatureNumbersetRange: GraphFeature, CustomStringConvertible { // <--- get the error here
...
}

I suspect that I don't need to explicitly conform to a protocol when I implement var description: String { get }, or whatever methods the protocol requires. Should I just follow fixit instructions and remove all these? Does Swift now automatically infer the conformance if a class implements all the protocol's methods?

解决方案

You'll get that error message in Xcode 7 (Swift 2) if a subclass declares conformanceto a protocol which is already inherited from a superclass. Example:

class MyClass : CustomStringConvertible {
    var description: String { return "MyClass" }
}

class Subclass : MyClass, CustomStringConvertible {
    override var description: String { return "Subclass" }
}

The error log shows:

main.swift:10:27: error: redundant conformance of 'Subclass' to protocol 'CustomStringConvertible'
class Subclass : MyClass, CustomStringConvertible {
                          ^
main.swift:10:7: note: 'Subclass' inherits conformance to protocol 'CustomStringConvertible' from superclass here
class Subclass : MyClass, CustomStringConvertible {
      ^

Removing the protocol conformance from the subclass declarationsolves the problem:

class Subclass : MyClass {
    override var description: String { return "Subclass" }
}

But the superclass must declare the conformance explicitly, it isnot automatically inferred from the existence of the descriptionproperty.

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