Flutter async/await 在 for Each 中不起作用

Question

我不知道这里缺少什么。。这是一个假定为向客户下订单的函数。整个逻辑很简单：

如果购物车中有一个项目，则只执行一次。如果有更多订单，则将订单追加到第一个订单号。但由于某些原因，它最初没有等到orderRepo.addOrder执行完成。

dynamic firstOrderNumber = 0;
var existingOrder = false;
void addOrder(List<Cart> carts) async {        --> Coming to add the list of orders
carts.forEach((_cart) async {                --> Going to add each items in cart

x += 1;
print("nVALUE of x inside addOrder = $x");     -> Adding X flag here to check
Order _order = new Order();
_order.productOrders = new List<ProductOrder>();
_order.tax = _cart.product.store.defaultTax;
_order.deliveryFee = payment.method == 'Pay on Pickup'
? 0
: _cart.product.store.deliveryFee;
OrderStatus _orderStatus = new OrderStatus();
_orderStatus.id = '1'; 
_order.orderStatus = _orderStatus;
_order.deliveryAddress = payment.method == 'Pay on Pickup'
? new Address()
: settingRepo.deliveryAddress.value;
_order.hint = ' ';
ProductOrder _productOrder = new ProductOrder();
_productOrder.quantity = _cart.quantity;
_productOrder.price = _cart.product.price;
_productOrder.id = _cart.product.id;
_productOrder.product = _cart.product;
_productOrder.options = _cart.options;
_order.productOrders.add(_productOrder);
print("Current value of EXISTING : $existingOrder");
if (!existingOrder) {
print("nnEntering not existing order....n");
await orderRepo.addOrder(_order, this.payment).then((value) {      ---> Doesn't wait. PROBLEM
if (value is Order) {
print("The value is now $value");
firstOrderNumber =
value.id.toString(); //catching order number to append
print("FIRSTORDERNUMBER : $firstOrderNumber");
setState(() {
loading = false;
});
}
});
print("Settting value of existing order now...");
existingOrder = true;
print("Existing order is now $existingOrder");
}
// print("Existing order is now $existingOrder");
else {
print("nnEntering existing order....n");
orderRepo
.addAdditionalOrder(
_productOrder, _cart, _order, firstOrderNumber, this.payment)
.then((value) {
if (value is Order) {
setState(() {
loading = false;
});
}
});
}
});
}

控制台输出：

I/flutter ( 6925): VALUE of x inside addOrder = 1
I/flutter ( 6925): Current value of EXISTING : false
I/flutter ( 6925): Entering not existing order....
I/flutter ( 6925): VALUE of x inside addOrder = 2    ---> See the problem. It came back to increment X before the await is complete.  
I/flutter ( 6925): Current value of EXISTING : false
I/flutter ( 6925): Entering not existing order....   

//现在，它给出了之前应该等待的AWAIT结果。。。。。

I/flutter ( 6925): The response of first order is : <JSON RESPONSE from first addOrder execution...coming late..>
I/flutter ( 6925): The value is now Instance of 'Order'
I/flutter ( 6925): FIRSTORDERNUMBER : 141
I/flutter ( 6925): Settting value of existing order now...
I/flutter ( 6925): Existing order is now true
I/flutter ( 6925): The response of first order is : 

有什么提示吗？在await orderRepo.addOrder(_order, this.payment).then((value) {完成之前，我怎么能不执行其他任何事情？？？已经试错好几天了

Answer 1

尝试map((像这个

await Future.wait(carts.map((_cart)async{
//your code here

}));

Answer 2

我认为它应该适用于您！

myFunc() async {
for(File file in files) {
await saveFiles(file);
}
}

Answer 3

解决了我的问题。

for (var item in items) {
await function(item);
}

Answer 4

使用then函数的实例只需使用await。

if (!existingOrder) {
print("nnEntering not existing order....n");
var value = await orderRepo.addOrder(_order, this.payment);
if (value is Order) {
print("The value is now $value");
firstOrderNumber = value.id.toString();
print("FIRSTORDERNUMBER : $firstOrderNumber");
setState(() {
loading = false;
});
}
print("Settting value of existing order now...");
existingOrder = true;
print("Existing order is now $existingOrder");
}