how to check condition with "" in swift 3.0

Question

I want to check that the maxprice is equal to "" this or not if it's "" then maxprice will become maxprice = 0

my Json

price = ({
    maxprice = "<null>";
    minprice = "<null>";
});

code

var Arr = NSArray()

Arr = result.value(forKey: "price") as! NSArray
let max = Arr.value(forKey: "maxprice")

if max == nil {
    self.MaxValue = 0
    self.MinValue = 0
}

else {
    let maxval =  (Arr.object(at: 0) as AnyObject).value(forKey: "maxprice") as! NSNumber
    let min =  (Arr.object(at: 0) as AnyObject).value(forKey: "minprice") as! NSNumber

    self.MaxValue = maxval
    self.MinValue = min
}

Error: Could not cast value of type 'NSNull' (0x102148918) to 'NSNumber' (0x10311c4a8).

if you want string as "" (empty) then you can use string.isEmpty (Check this question https://stackoverflow.com/questions/24133157/check-empty-string-in-swift) — Kamaldeep singh Bhatia, Sep 18 '17 at 06:28
If you mean literally the string `` you can just check `if max == ""`. If you mean the Swift value nil, you should use a null coalescing operator: `MaxValue = blahblah ?? 0` — charles-allen, Sep 18 '17 at 06:34
Actually throwing any non-numeric string into `as? Int` will result in `nil`, so that's probably the way to go. — charles-allen, Sep 18 '17 at 06:45
This is Swift. Do not use `NSArray`, this avoids a horrible syntax like `... as AnyObject).value(forKey: "maxprice")` and do not use `valueForKey` unless you can explain why you need KVC. And why `NSNumber`? There are native types (`Int`, `Double`) in Swift — vadian, Sep 18 '17 at 06:46

score 12 · Answer 1 · answered Sep 18 '17 at 06:35

12

You can also use is to check for the presence of a null:

if Arr.value(forKey: "maxprice") is NSNull {
    // do something with null JSON value here
}

answered Sep 18 '17 at 06:35

AshokPolu

645
5
12

Is this ObjectiveC style? I think in Swift you want `if Blah == nil { ... }`, or better yet, unbox the optional at the same time using `if let unboxed = Blah { // use unboxed }` – charles-allen Sep 18 '17 at 06:43
this is checking the value is null or not in swift. – AshokPolu Sep 18 '17 at 06:44

score 3 · Answer 2 · answered Sep 18 '17 at 06:38

3

Swift 3.0

You can get this in short line of code using ?? as like below also we can say rescue operation.

let max = Arr.value(forKey: "maxprice") as? NSNumber ?? 0

answered Sep 18 '17 at 06:38

Jaydeep Vora

6,085
1
22
40

vadian · Answer 3 · 2017-09-18T07:31:12.700

This is the Swift way.

Use optional bindings and do not use objectivecish NSArray, valueForKey and NSNumber

You need to check

if the value for key price is a Swift array of dictionaries ([[String:Double]]). The distinct type avoids the extra check for NSNull
if the array is not empty.

Assuming minprice and maxprice are supposed to be Double values, if not replace Double with Int

if let priceArray = jsonDict["price"] as? [[String:Double]],
    let price = priceArray.first {
    minValue = price["minprice"] ?? 0.0
    maxValue = price["maxprice"] ?? 0.0
} else {
    minValue = 0.0
    maxValue = 0.0
}

how to check condition with "" in swift 3.0

3 Answers3