Filter out objects in an array in Swift

Question

I've got var campaigns: [Campaign] = [] Campaign objects have a property published. I'd like to map through the array and filter out unpublished campaigns so that the result is an array holding published campaigns only I've tried below but get of course get 'nil' is incompatible with return type 'Campaign'

self.campaigns = self.campaigns.map({ (campaign) -> Campaign in
                        if campaign.published == 1 {
                            return campaign
                        } else {
                            return nil
                        }
                    })

Anyone knowing the solution to this mini-problem? Thanks ;-)

If your goal is to filter self.campaigns, why don't you call filter? Is there some good reason why you cannot call it? self.campaigns = self.campaigns.filter {$0.published == 1} or whatever — matt
– matt, Commented Jan 29, 2020 at 17:07
It's ironic that you have mentioned the word filter in your question and you are not using it. Try what @matt said, if it still didn't work do share the Object and we will help you figure out. — Rob
– Rob, Commented Jan 29, 2020 at 17:12

flanker · Accepted Answer · 2020-01-29 17:14:20Z

2

To do it your way you'd need to use compactMap in order to drop the nil responses, however you'd be better off just using filter

campaigns = campaigns.filter{$0.published == 1}

answered Jan 29, 2020 at 17:14

flanker

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4 Comments

gadu Over a year ago

this ^ map should really only be used when changing the type. compactMap is kind of like a map + filter so not preferred since the resulting type is the same in your example

Leo Dabus Over a year ago

There is a mutating method called removeAll(where:) on RangeReplaceableCollection exactly for that. campaigns.removeAll { $0.published != 1}

Bernhard Engl Over a year ago

Thanks @flanker for the solution. Got so stuck with map that I didn't consider to look for other functions to solve my problem :-(

Bernhard Engl Over a year ago

Thanks @Leo Dabus for the alternative approach!!

Mashood Murtaza · Accepted Answer · 2020-01-29 19:41:19Z

0

Agreed with @flanker answer Use compactMap that returns an array containing the non-nil results of calling the given transformation with each element of this sequence.

self.campaigns = self.campaigns.compactMap({ $0.published == 1 ? $0 : nil })

edited Jan 29, 2020 at 19:41

answered Jan 29, 2020 at 19:06

Mashood Murtaza

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2 Comments

vadian Over a year ago

Your code doesn't compile because the result of compactMap is an array of Bool (and after the edit an array of Int)

vadian Over a year ago

Nope, compactMap is wrong anyway, it transforms the type to another. The returned type of the closure must be Campaign , It works with { $0.published == 1 ? $0 : nil} but this is a cumbersome version of filter.

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