如何使用咖啡腳本實現觀察者

Question

我嘗試在咖啡腳本中實現觀察者模式，如wikipedia observer pattern。這怎麼可以用coffeescript完成？

Answer 1

創建一個類是這樣的：

class Observer 
    constructor:() -> 
    @subscribers = {} 
    notify: (to, arg...) -> 
    if @subscribers[to] 
     for cb in @subscribers[to].callback 
     try 
      cb.apply @,[to].concat arg 
     catch err 
      console.log to+" "+(arg?.join ', ')+": "+err 
    subscribe: (to, cb) -> 
    if @subscribers[to]==undefined || @subscribers[to].callback.size==0 
     @subscribers[to]={'callback':[cb]} 
    else 
     @subscribers[to].callback.push cb if cb not in @subscribers[to].callback 
    unsubscribe: (to, cb) -> 
    @subscribers[to]?.callback.splice @subscribers[to].callback.indexOf(cb), 1 

如何使用

### Define subscriber ### 
class SubscriberA 
    onEvent: (item) -> 
    console.log item 

class SubscriberB 
    onEvent: (item) -> 
    console.log item 

class SubscriberC 
    onEventTypeA: (item) -> 
    console.log "EventTypeA: "+item 

    onEventTypeB: (item) -> 
    console.log "EventTypeB: "+item 

class SubscriberD 
    onEventTypeA: (item,arg="23 is default") -> 
    console.log item+" "+arg 
    onEventTypeB: (item,arg...) -> 
    console.log item + " with: " 
    for a in arg 
     console.log a 

### Create observer ### 
myO = new Observer() 

### Create subscribing objects 
    In real live this would be your objects that will have to provide a function that handels notifications. Within this example they are called onEventXYZ 
### 
subscriptionOfA = new SubscriberA() 
subscriptionOfB = new SubscriberB() 
subscriptionOfC = new SubscriberC() 
subscriptionOfD = new SubscriberD() 

console.log ": Subscribe Peter once and Paul twice" 
myO.subscribe "Peter", subscriptionOfA.onEvent 
myO.subscribe "Paul", subscriptionOfA.onEvent 
myO.subscribe "Paul", subscriptionOfA.onEvent 

console.log ": Notify Peter and Paul" 
myO.notify "Peter" 
myO.notify "Paul" 

console.log ": Paul is only notified once as duplicate subscriptions are ignored while subscribe" 
console.log ": Subscribe Paul with a different subscriber" 
myO.subscribe "Paul", subscriptionOfB.onEvent 
console.log ": Notify Peter and Paul" 
myO.notify "Peter" 
myO.notify "Paul" 

console.log ": Paul is notified twice as two different subscriptions are subscribed" 

console.log "\n: Unsubscribe Peter" 
myO.unsubscribe "Peter" 
console.log ": Notify Peter and Paul" 
myO.notify "Peter" 
myO.notify "Paul" 


console.log "\n: Not subscribed items will be ignored at notify" 
console.log ": Notify Bob" 
myO.notify "Bob" 

console.log "\n: You may use multiple eventHandler in your subsribers" 

myO.subscribe "Mary", subscriptionOfC.onEventTypeA 
myO.subscribe "Jane", subscriptionOfC.onEventTypeB 

console.log ": Notify Mary and Jane" 
myO.notify "Mary" 
myO.notify "Jane" 

console.log "\n: You may use arguments with your eventHandler" 

myO.subscribe "Laurel", subscriptionOfD.onEventTypeA 
myO.subscribe "Hardy", subscriptionOfD.onEventTypeB 

console.log ": Notify Laurel without argument" 
myO.notify "Laurel" 
console.log ": Notify Laurel with argument" 
myO.notify "Laurel", 42 
console.log ": Notify Hardy with multiple arguments" 
myO.notify "Hardy", "Argument String",1,2,3,['a','b']