AngularJS：具有承諾數據和非承諾數據的函數

Question

我有一個函數，它具有承諾數據和簡單數學值的組合數據。這裏的功能：

_getTotalPrice = function() { 

      var price = 0; 
      // Simple Math data. 
      // Calculate price for channels first. 
      price = price + (num_channels - 5)*(4); 


      var themepacks = cart.themepacks; 
      if(themepacks) { 
       angular.forEach(themepacks, function(pack, index) { 

       // data coming from a service 
       channelFactory.getThemePack(pack).then(function(result) { 
        price = price + Number(result.packPriceAmt); 
        console.log("price", price); 
        }); 
       }); 
      } 

      console.log(" Total price", price); 
      return price; 
}; 

在頁面加載的時間，Total price和price是不同的價值。這是因爲承諾解決後，price被加載。在返回值之前如何等待承諾解決？我是否在這個功能中創造了另一個承諾？

Answer 1

該函數本身必須返回總價格的承諾，該總價格取決於創建的承諾分辨率的所有（all）。

首先，小保將幫助它清除掉：

// return a promise for a theme pack price 
function priceOfPack(pack) { 
    return channelFactory.getThemePack(pack).then(function(result) { 
     return Number(result.packPriceAmt); 
    }); 
} 

這使得更清楚的是，我們要收集一套的價格異步的想法。現在的循環是簡單...

_getTotalPrice = function() { 
    var themepacks = cart.themepacks || []; 
    var promises = []; 
    angular.forEach(themepacks, function(pack, index) { 
     promises.push(priceOfPack(pack)); 
    }); 
    var basePrice = (num_channels - 5) * 4; 

    // when all promises are resolved, they will be with an array of prices 
    return $q.all(promises).then(function(result) { 
     return result.reduce((a, b) => { a + b }, basePrice); 
    }); 
} 

調用者必須認識到，新的函數返回一個承諾，並相應地改變，所以......

_getTotalPrice().then(function(result) { 
    // result is the totalPrice 
}); 

Answer 2

試試這個：

_getTotalPrice = function() { 

      var price = 0; 
      // Simple Math data. 
      // Calculate price for channels first. 
      price = price + (num_channels - 5)*(4); 


      var themepacks = cart.themepacks; 
      if(themepacks) { 
       angular.forEach(themepacks, function(pack, index) { 

       // data coming from a service 
       return channelFactory.getThemePack(pack).then(function(result) { 
        price = price + Number(result.packPriceAmt); 
        return $q.when(price); 
        }); 
       }); 
      } 
      else{ 
       return $q.when(price); 
      } 
}; 

_getTotalPrice().then(function(price){ 
    console.log(price); 
}); 

這將是異步功能。