Swift 4 Struct Searching by parameter with contains

Question

I have array of structs and I don't know really how to use search by one of the struct's parameter.

My struct looks like:

struct Actor {
   var name: String!
   var posterURL: String!

    init(_ dictionary: [String: Any]) {
       name = dictionary["name"] as! String
       posterURL = dictionary["image"] as! String
    }
}

So, I've tried to use predicate

let actorSearchPredicate = NSPredicate(format: "name contains[c] %@", text)
filterredActors = (actors as NSArray).filtered(using: actorSearchPredicate)

But, when I'm trying to type anything, it crashes with error

[<_SwiftValue 0x10657ffb0> valueForUndefinedKey:]: this class is not key value coding-compliant for the key name.'

What is the right way of using predicate search with structs? Thank you

Why bother with NSPredicate? actors.filtered{ $0.name.contains(text) } — Alexander
– Alexander, Commented Jan 12, 2018 at 20:09
Only thing missing with $0.name.contains(text) is making it case insensitive. — creeperspeak
– creeperspeak, Commented Jan 12, 2018 at 20:19
One really easy way of making it case insensitive is $0.name.lowercased().contains(text.lowercased()). — creeperspeak
– creeperspeak, Commented Jan 12, 2018 at 20:23
Why are you casting as AnyObject? You shouldn't be using that at all in Swift 4. Try actors.filtered{( $0.name.lowercased().contains(text.lowercased()) )}. Also, there is a difference between filter and filtered. Make sure you're using filtered. — creeperspeak
– creeperspeak, Commented Jan 12, 2018 at 20:40

vadian · Accepted Answer · 2018-01-13 10:59:20Z

3

NSPredicate is not needed, Swift got convenience methods to check case insensitive

whether the receiver contains a given string by performing a case insensitive, locale-aware search.

filterredActors = actors.filter { $0.name.localizedCaseInsensitiveContains(text) }

and case and diacritic insensitive

whether the receiver contains a given string by performing a case and diacritic insensitive, locale-aware search.

filterredActors = actors.filter { $0.name.localizedStandardContains(text) }

answered Jan 13, 2018 at 10:59

vadian

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Comments

djromero · Accepted Answer · 2018-01-13 13:56:09Z

If you need to use a predicate to filter structs, you can do it without going into @objc territory or converting your data into NSArray:

func filter(actors: [Actor], named: String) -> [Actor] {
    let predicate = NSPredicate(format: "SELF contains[cd] %@", named)
    return actors.filter {
        predicate.evaluate(with: $0.name)
    }
}

Example:

struct Actor {
    let name: String
    let imdb: String
}

let actors = [
    Actor(name: "John Travolta", imdb: "http://www.imdb.com/name/nm0000237"),
    Actor(name: "Uma Thurman", imdb: "http://www.imdb.com/name/nm0000235"),
    Actor(name: "Samuel L. Jackson", imdb: "http://www.imdb.com/name/nm0000 168"),
    Actor(name: "Penélope Cruz", imdb: "http://www.imdb.com/name/nm0004851"),
    Actor(name: "Penelope Ann Miller", imdb: "http://www.imdb.com/name/nm0000542")
]

print(filter(actors: actors, named: "Uma").map { $0.name })
// ["Uma Thurman"]
print(filter(actors: actors, named: "J").map { $0.name })
// ["John Travolta", "Samuel L. Jackson"]

Filtering using a predicate is useful, for example, to take into account diacritics. Let's search an actor name with an accented character:

print(filter(actors: actors, named: "Penelope").map { $0.name })
// ["Penélope Cruz", "Penelope Ann Miller"]

It finds both "Penelope", with and without accented "e".

Using String.contains won't work in that case:

let text = "Penelope"
let hits = actors.filter { ( $0.name.lowercased().contains(text.lowercased()) )}
print(hits.map { $0.name })
// ["Penelope Ann Miller"]

There are better alternatives (String localized search, regular expressions, String.range(of:options:range:locale), ...). Using predicates is not faster (not much slower either). It may be easier to reason about complex queries using predicate syntax if you already know it.

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