How to check if array contain null value and give default value swift

Question

I have an array that's populated from a JSON response from an API server. Sometimes the values for a key in this array are Null

I am trying to take the given value and drop it into the detail text of a table cell for display.

The problem is that when I try to coerce the value into an String I get a crash, which I think is because I'm trying to coerce Null into a string.

What's the right way to do this? ex- my response is below type and I'm trying to fetch that array in self.imageArray variable

response = ["abc.jpg","null","xyzzy.jpg"]

 self.imageArray = (self.dataArray.value(forKey: "product_image") as? [String])!

but at second iteration it gets crashed coz second value is null.

Perform your iteration using compactMap. It can handle nil value. - developer.apple.com/documentation/swift/sequence/… — Pratik Sodha
– Pratik Sodha, Commented Oct 14, 2019 at 7:30

Nahid Raihan · Accepted Answer · 2019-10-14 07:41:55Z

1

In your case only (Solution according to given question 'response' array) :-

response = ["abc.jpg","null","xyzzy.jpg"]

Use following code

      if !response.contains("") && !response.contains("null"){
        //  No null or empty string now
        // your code
      }else{
           print("Contain null or empty value")
       }

edited Oct 14, 2019 at 7:41

answered Oct 14, 2019 at 7:36

Nahid Raihan

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2 Comments

Anbu.Karthik Over a year ago

how will you validate " " empty string

Nahid Raihan Over a year ago

@Anbu.Karthik Bro ,first of all , this type of response are not good practice (my opinion) . If ur Back end developer can't manage this then you have to trim the all value of array string and then do like answer code . You can trim string like : let trimmedString = string.trimmingCharacters(in: .whitespaces) . This is actually what I will do in this scenario. It might be handle more optimize way .

Anbu.Karthik · Accepted Answer · 2019-10-14 07:42:29Z

1

You can user compatcMap in this case.

 let response = ["abc.jpg", nil, "xyzzy.jpg"]
 let result = response.compactMap { $0 }
 print(result)

If you are sure the value will be "null" in string type then you can use the following way.

let response = ["abc.jpg", "null", "xyzzy.jpg"]
let result = response.filter { $0 != "null" }
print(result)

the combined result is

 let result = response.filter { $0 != "null" }.compactMap { $0 }
print(result)

edited Oct 14, 2019 at 7:42

Anbu.Karthik

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answered Oct 14, 2019 at 7:31

Mahendra

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1 Comment

Anbu.Karthik Over a year ago

how will you validate "null" this type string of null .. ?

Muhammad Shauket · Accepted Answer · 2019-10-14 07:58:17Z

1

This will handle the issue for both null and nil.

response = ["abc.jpg","null","xyzzy.jpg", nil]
var result = response.filter { return ($0 != "null" && $0 != nil) }

print(result) // return option result.

edited Oct 14, 2019 at 7:58

answered Oct 14, 2019 at 7:41

Muhammad Shauket

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5 Comments

Starsky Over a year ago

That is iteration through the array twice. Not very good performance-wise. What if his array has 5000 items?

Starsky Over a year ago

Now it is better, but as someone posted a comment in an another answer: what if there is an object like this: " "? :)

Muhammad Shauket Over a year ago

then you can add one more check the same as the other.

pallavi Over a year ago

@ Shauket Sheikh- I get a crashes

Muhammad Shauket Over a year ago

Whats the response array?

Ankur Lahiry · Accepted Answer · 2019-10-14 07:41:51Z

0

It should be like

var image = ["abc.jpg", nil, "xyzz.jpg"]
image = image.filter { $0 != nil}
print(image)

You have to filter out the nil values.

if you remove specific string "null"

var image = ["abc.jpg", "null", "xyzz.jpg"]
image = image.filter { $0 != "null"}
print(image)

edited Oct 14, 2019 at 7:41

answered Oct 14, 2019 at 7:33

Ankur Lahiry

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2 Comments

Anbu.Karthik Over a year ago

how will you validate "null" this type string of null .. ?

Ankur Lahiry Over a year ago

Contact with your backend, it is their fault. "null" is a valid string.

Starsky · Accepted Answer · 2019-10-14 08:43:26Z

0

If you know for sure that a valid value will always contain an image type like .jpg, then you can check against that and it will remove nil values, "null" or any other random strings, including empty strings " ".

response = ["abc.jpg","null","xyzzy.jpg", nil, " "]
self.imageArray = response.filter { $0?.contains(".jpg") ?? false }

edited Oct 14, 2019 at 8:43

answered Oct 14, 2019 at 8:09

Starsky

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3 Comments

pallavi Over a year ago

Could not cast value of type 'NSNull' (0x10ea06e48) to 'NSString' (0x10d5554a8). I get this error

pallavi Over a year ago

@ Starsky- I can't fetch array from response because of null value.it crashes

Starsky Over a year ago

You can assign to your self.imageArray directly the filtered version of response. If it still has issues, then can you post a bigger portion of your code, where you handle your request response and you try to parse that JSON?

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