swift - The Chain Responsibility pattern
|
The chain of responsibility pattern is useful when there are multiple objects that could take responsibility for a request but you don’t want to expose details of those objects to the calling component. 责任链模式:把两种/多种解决方案封装到到一个链里，提供一个封闭的接口一一尝试。
let messages = [ Message(from:"bob@example.com",to:"joe@example.com", subject:"Free for lunch?"), Message(from:"joe@example.com",to:"alice@acme.com", subject:"New Contracts"),19)"> Message(from:"pete@example.com",to:"all@example.com", subject: "Priority: All-Hands Meeting"), ]; iflet chain =Transmitter.createChain(true) { for msgin messages { let handled = chain.sendMessage(msg); println("Message sent:(handled)"); } } //1 struct Message { let from:String; let to:String; let subject:String; }
//2
class Transmitter { var nextLink:Transmitter?;
required init() {}
func sendMessage(message:Message,handled:Bool =false) ->Bool { if (nextLink !=nil) { returnnextLink!.sendMessage(message,handled: handled); }elseif (!handled) { println("End of chain reached. Message not sent"); } return handled; }
classfunc createChain(localOnly:Bool) ->Transmitter? {
let transmitterClasses:[Transmitter.Type] = localOnly ? [PriorityTransmitter.self,LocalTransmitter.self] : [PriorityTransmitter.self,LocalTransmitter.self,RemoteTransmitter.self];
var link:Transmitter?;
for tClassin transmitterClasses.reverse() { let existingLink = link; link = tClass(); link?.nextLink = existingLink; }
return link; } privateclassfunc matchEmailSuffix(message:Message) ->Bool { iflet index =find(message.from,"@") { return message.to.hasSuffix(message.from[Range<String.Index>(start: index,end: message.from.endIndex)]); } return false; } } class LocalTransmitter :Transmitter {
overridefunc sendMessage(message:Message,var handled:Bool) ->Bool { if (!handled &&Transmitter.matchEmailSuffix(message)) { println("Message to(message.to) sent locally"); handled =true; } returnsuper.sendMessage(message,handled: handled); } } class RemoteTransmitter :Transmitter {
overridefunc sendMessage(message:Message,var handled:Bool) ->Bool { if (!handled && !Transmitter.matchEmailSuffix(message)) { println("Message to(message.to) sent remotely"); handled =true; } returnsuper.sendMessage(message,handled: handled); } } class PriorityTransmitter :Transmitter { var totalMessages =0; var handledMessages =0;
overridefunc sendMessage(message:Message,var handled:Bool) ->Bool { totalMessages++; if (!handled && message.subject.hasPrefix("Priority")) { handledMessages++; println("Message to(message.to) sent as priority"); println("Stats: Handled(handledMessages) of(totalMessages)"); handled =true; } returnsuper.sendMessage(message,handled: handled); } } （编辑：李大同） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |