Swift新特性整理

概述  编译警告 运行时警告会打印在控制台： ***Swift runtime: ClassName.swift:lineInFile:columnInLine: entrypoint -[ClassName methodName] generated by implicit @objc inference is deprecated and will be removed in Swift 4;

编译警告

运行时警告会打印在控制台：

***Swift runtime: Classname.swift:lineInfile:columnInline: entrypoint -[Classname methodname] generated by implicit @objc inference is deprecated and will be removed in Swift 4; add explicit @objc to the declaration to emit the Objective-C entrypoint in Swift 4 and suppress this message

同样：想要修复运行时警告，需要添加 @objc 修饰符到对应的方法或者符号。

运行时警告的常见原因:

在 OC 中使用 SEL 在 swift 中使用了 perform methods 在 OC 中使用了 performSelector methods 使用了 @IBOutlet 或者 @IBAction 其他修改 NSAttributedStringKey

swift3.xpublic init(string str: String,attributes attrs: [AnyHashable : Any]? = nil)swift4.0public init(string str: String,attributes attrs: [NSAttributedStringKey : Any]? = nil)

String

废弃characters

swift 3var count = string.characters.counterror'characters' is deprecated: Please use String or Substring directlyswift 4count = string.count

废弃addingPercentEscapes

swift 3var url = @"http://www.example.com?username=姓名"url = url.addingPercentEscapes(using: String.EnCoding.utf8)!error'addingPercentEscapes(using:)' is unavailable: Use addingPercentEnCoding(withAllowedCharacters:) instead,which always uses the recommended UTF-8 enCoding,and which encodes for a specific URL component or subcomponent since each URL component or subcomponent has different rules for what characters are valID.swift 4uri = uri.addingPercentEnCoding(withAllowedCharacters: CharacterSet.urlqueryAllowed)!

废弃substring(to:)

swift 3let index = tagText.index(tagText.startIndex,offsetBy: MPMultipleStyleListItemTagMaxLength)// 警告：'substring(to:)' is deprecated: Please use String slicing subscript with a 'partial range upto' operator.let b = tagText.substring(to: index)Swift 4let a = tagText.prefix(upTo: index) //a 的类型是 Substring，不是 String

pod 引用

添加以下内容到 Podfile

post_install do |installer|    installer.pods_project.targets.each do |target|        if ['WTCarouselFlowLayout','XSLRevenue','OHhttpStubs/Swift'].include? target.name            target.build_configurations.each do |config|                config.build_settings['SWIFT_VERSION'] = '3.2'            end        end    endend

系统方法

UItableVIEwDelegate 协议方法名变更，没有错误提示：

// swift3.xfunc tableVIEw(_ tableVIEw: UItableVIEw,heightForRowAtIndexPath indexPath: IndexPath) -> CGfloat // swift4.0func tableVIEw(_ tableVIEw: UItableVIEw,heightForRowAt indexPath: IndexPath) -> CGfloat

总结

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