CODEWITHSUNDEEP
swift
Ackman
Ackman

Reputation: 1582

nil value handling in Swift

I am trying to build an orders array in Swift. Sometimes the values that get filled in them are nil. This leads to an app crash. Ho do I handle this?

In the code below, I loop through orders and add them to the orders array:

var orders: [order] = []
//loop
orders[i] = order(dispatchNumber: "\
(myOrder.DispatchNumber!)",orderId: "\
(myOrder.OrderId!)", source: myOrder.SourceName! , sourceAddress1: myOrder.SourceAddress! , 
    sourceAddress2: myOrder.SourceCity! + ", " + myOrder.SourceState! +
 " " + myOrder.SourceZip! , destination: myOrder.DestinationName!, 
destinationAddress1:myOrder.DestinationAddress!, destinationAddress2:
myOrder.DestinationCity! + ", " + myOrder.DestinationState! + " " +
 myOrder.DestinationZip! , loads: "\(myOrder.LoadCount!)",
 loadsDelivered: "\(myOrder.LoadsDelivered!)",  tons: "\

(myOrder.TonsCount!)", price: "$" + "\(myOrder.PayRate!)", sourceDistance: myOrder.DistanceToSource!, onewayDistance: myOrder.OrderLegDistance!,  pickupStart: myOrder.PickupBy!, earliestDelivery: myOrder.DeliverStart!,latestDelivery: myOrder.DeliverBy!,product: myOrder.ProductName! , loadsRemaining: "\(thisLoadsRemaining)", truckType: myOrder.TruckType!, notes:
 myOrder.Notes!, isStarted: myOrder.IsStarted, isOnHold: myOrder.IsOnHold, payRateType: "\(myOrder.PayRateType!)", 
isStayOn: myOrder.IsStayOn, customerName: myOrder.CustomerName! )

Sometimes myOrder.OrderLegDistance! gets a nil value. How do I handle it?

Upvotes: 0

Views: 2476

Answers (3)

CSjunkie
CSjunkie

Reputation: 555

The safe bet would be to check for nil before unwrapping.

var orderLegDistance = defaultValue if myOrder.OrderLegDistance != nil { orderLegDistance = myOrder.OrderLegDistance! }

You can use the same kind of check to determine that you need to ignore the value of myOrderLegDistance if your logic demands that.

EDIT Adding some additional unwrapping options here:

if let legDistance = myOrder.OrderLegDistance {
    orderLegDistance = legDistance
}

Or, as mentioned in a comment below:

orderLegDistance = myOrder.OrderLegDistance ?? defaultValue

Upvotes: 1

CZ54
CZ54

Reputation: 5588

Depends of your business rules :

  • If the OrderLegDistant is a mandatory value, you may want to 'forget' this order. In order to do that you can use a guard statement, to check all the mandatory params.

  • If theOrderLegDistant is not mandatory, update your model to have this attribute as Optional, and remove the unwrap (!) from your constructor.

Upvotes: 1

user3151675
user3151675

Reputation: 58019

It's generally a bad idea to use implicitly unwrapping. Always handle the values safely.

Use guard let or if let to make sure the variables have a value when you work with them.

if let distance = orderLegDistance {
    print("\(distance)")
}

guard let distance = orderLegDistance else {
    print("Error: distance is empty")

    return
}

Moreover, you can define a default value by using ??.

print("\(orderLegDistance ?? 0)") /*this will print 0 if orderLegDistance is empty*/

On a side note, always use camelCase variable names instead of PascalCase.

Upvotes: 3

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