Checking if array is nil or not

Question

I have a array of my custom model, and I want to check if it is not nil and its size is greater then 0.

Following is my array with custom object

var listCountries : [Countries]? = nil

now In viewDIdLoad I want to make a check on it. I am new to Swift. I have good experience in working in Java.

I have read out Optional values concept and guard, if let statements. But I am unable to understand how efficiently they may be used. I have read too much SO questions but failed to figure out.

for example , if I want to check the upper given array in java I have only to do

if(listCountries != null && listCountries.size()>0){
    //DO something 
}

So to summarize my question:

How to make the upper given(Java code) check in to swift 4.? What is more smooth and reliable way.
What is a use of if let , guard, guard let statements. if I declare a variable (array, string) as optional I have to bear optional check like force wrapping each and every place. This is for me so making too much confusion.

Please help. I know this question has been asked in different ways. But this has some different context.

Consider to declare the array as non-optional empty `var listCountries = [Countries]()`. — vadian, May 31 '18 at 10:42
https://stackoverflow.com/questions/24034483/what-is-an-unwrapped-value-in-swift — Midhun MP, May 31 '18 at 10:43
Check out the duplicate. It provides 9 ways of doing this; one for every taste! — vacawama, May 31 '18 at 11:05

score 8 · Accepted Answer · answered May 31 '18 at 10:42

Just use ??.

if !(listCountries ?? []).isEmpty {

However, since you want to probably use listCountries in the if block, you should unwrap

if let listCountries = self.listCountries, !listCountries.isEmpty {

Ideally, if nil and empty means the same to you, don't even use an optional:

var listCountries: [Countries] = []

score 5 · Answer 2 · answered May 31 '18 at 10:42

5

I would do it something like...

if let list = listCountries, !list.isEmpty { // Can also use list.count > 0
    // do something
}

Even though you are not using the list inside the braces you are still using the list in the condition.

Or, like Sulthan said... make it non-optional to begin with if it makes no difference.

answered May 31 '18 at 10:42

Fogmeister

76,236
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1

Again, you're the first :D – Ahmad F May 31 '18 at 10:47

Ahmad F · Answer 3 · 2018-05-31T10:53:19.057

Obviously, I would assume that you are able to recognize the difference between nil array and empty array.

So, if we tried to implement a literal translation to your question:

I want to check if it is not nil and its size is greater then 0

For the first condition:

// "I want to check if it is not nil":
if let unwrappedList = listCountries {
    // ...
}

and for the second condition:

// "I want to check if it is not nil":
if let unwrappedList = listCountries {
    // "and its size is greater then 0":
    if !unwrappedList.isEmpty {
        // ...
    }
}

However, you could combine both of the conditions by using the comma to achieve the multi-clause condition:

// I want to check if it is not nil and its size is greater then 0
if let unwrappedList = listCountries, !unwrappedList.isEmpty {
    // ...
}

Or by using guard statement:

// I want to check if it is not nil and its size is greater then 0
guard let unwrappedList = listCountries, !unwrappedList.isEmpty else {
    return
}

AbecedarioPoint · Answer 4 · 2018-05-31T10:53:13.460

-1

if let list = listCountries {
    if(!list.isEmpty && list.count > 0) {
            //value   
        }
}

edited May 31 '18 at 10:53

answered May 31 '18 at 10:43

AbecedarioPoint

197
9

Both conditions are redundant. – vadian May 31 '18 at 10:43
list countries is optional you can't do that before unwrap – U. Benlice May 31 '18 at 10:44
@U.Benlice; @vadian Thank you for pointing me out. – AbecedarioPoint May 31 '18 at 10:48

Checking if array is nil or not

4 Answers4