How to Flatten Array of Array of custom Object [[CustomModel?]]?

Question

I've only basic knowledge in Swift. I want to change var dataSource:[[CustomModel?]]? into [CustomModel].

I tried following Methods

let flat = dataSource.reduce([],+)
let flat = dataSource.flatMap { $0 }
let flat = dataSource.compactMap{ $0 }
let flat = dataSource.Array(dataSource.joined())

I'm getting error

Cannot convert value of type '[FlattenSequence<[[CustomModel?]]>.Element]' (aka 'Array<Optional< CustomModel >>') to expected argument type '[CustomModel]'

you can't change the type of the same variable you have to create another 1 — Shehata Gamal
– Shehata Gamal, Commented Jul 8, 2020 at 11:47
reduce flatMap compactMap return a value and you don't assign it to another variable so your first 3 lines are useless — Shehata Gamal
– Shehata Gamal, Commented Jul 8, 2020 at 11:53

Shashank Mishra · Accepted Answer · 2020-07-08 13:21:28Z

5

You need to flat the nested array first using flatMap{}, then in order to get the non-optional value use compactMap{}. Suppose the input array is [[Int?]]

let value:[Int] = dataSource.flatMap{$0}.compactMap{ $0 } //Correct

The other option will give an error -

let value:[Int] = dataSource.flatMap{ $0 } ?? [] //Error

//Correct

//Wrong

answered Jul 8, 2020 at 13:21

Shashank Mishra

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Shehata Gamal · Accepted Answer · 2020-07-08 11:55:52Z

3

You can try

var arr:[CustomModel] = dataSource?.flatMap { $0 } ?? []

Also

var arr:[CustomModel] = dataSource?.flatMap { $0 }.compactMap{ $0 } ?? []

edited Jul 8, 2020 at 11:55

answered Jul 8, 2020 at 11:43

Shehata Gamal

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