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      1 /**
      2  * PriceCache
      3  */
      4 function PriceCache() {
      5 }
      6 
      7 PriceCache.prototype = {
      8 	getCachedPrice: function(instrumentId) {
      9 	},
     10 	setCachedPrice: function(instrumentId, price) {
     11 	}
     12 }
     13 
     14 /**
     15  * PriceFetcher
     16  */
     17 function PriceFetcher() {
     18 }
     19 
     20 PriceFetcher.prototype = {
     21 	getPriceFromServer: function(instrumentId) {
     22 	}
     23 }
     24 
     25 
     26 /**
     27  * PriceService
     28  */
     29 function PriceService(priceFetcher, priceCache) {
     30 	this._priceFetcher = priceFetcher;
     31 	this._priceCache = priceCache;
     32 }
     33 
     34 PriceService.prototype = {
     35 	getPrice: function(instrumentId) {
     36 		var price = this._priceCache.getCachedPrice(instrumentId);
     37 		if(price==null) {
     38 			price = this._priceFetcher.getPriceFromServer(instrumentId);
     39 			this._priceCache.setCachedPrice(instrumentId, price);
     40 		}
     41 		return price;
     42 	}
     43 }
     44