CODEWITHSUNDEEP
iosswiftcastingoption-type
Bagdat
Bagdat

Reputation: 328

'[Double?]' is not convertible to '[Double]'

maybe question is so silly but i am new in iOS
how can I convert optional to non-optional data array

[Double?] is not convertible to [Double]

Here is line with error

   let massive = [dictionary[j]![one]?.doubleValue] as [Double]

I am converting to [Double] because i am using it here

let dataEntry = BarChartDataEntry(values: massive, xIndex: c)

And it throws error

Cannot invoke initializer for type 'BarChartDataEntry' with an argument list of type '(values: [Double?], xIndex: Int)'

contructor of class BarChartDataEntry is like that

public init(values: [Double], xIndex: Int)

Upvotes: 1

Views: 646

Answers (2)

Dan Beaulieu
Dan Beaulieu

Reputation: 19954

[Double?] is wrapped, you have to unwrap it in order to use it as a [Double]. To better understand, take a look at what your Doubles are wrapped with:

enum Optional<T> {
    case None // has no value
    case Some(T) // has some value 
}

So you need to unwrap your optionals in order to use them as non-optional [Double].

One option, is that you can perform a flatMap operation on your optional array which will convert your [Double?] to a [Double]. Bear in mind that flatMap will copy your array and replace it, so if you're performing a flatMap on a very large array you might run into issues.

Here's a playground ready example:

var dubs : [Double?] = [1.2,1.4]

print(dubs) // [{Some 1.2}, {Some 1.4}]

var newDubs = dubs.flatMap { dub in
    return dub
}

print(newDubs) // [1.2, 1.4]

Upvotes: 2

user5617868
user5617868

Reputation:

It depends on what your value for your double is. In this case, you must be sure that it has a decimal point, and is not 0.0. In which case, you can put your code as 

//your code
... = Double[...]

It should resolve. Else, please provide some code so I can suggest a way to resolve. Hope this works for you :)

Upvotes: 0

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