I am trying to filter an array of dictionaries. The below code is the sample of the scenario i am looking for
let names = [
[ "firstName":"Chris","middleName":"Alex"],
["firstName":"Matt","middleName":""],
["firstName":"John","middleName":"Luke"],
["firstName":"Mary","middleName":"John"],
]
The final result should be an array for whom there is a middle name.
This did the trick
names.filter {
if let middleName = $0["middleName"] {
return !middleName.isEmpty
}
return false
}
Slightly shorter:
let result = names.filter { $0["middleName"]?.isEmpty == false }
This handles all three possible cases:
$0["middleName"]?.isEmpty evaluates to false and the predicate
returns true.$0["middleName"]?.isEmpty evaluates to true and the predicate
returns false.$0["middleName"]?.isEmpty evaluates to nil and the predicate
returns false (because nil != false).You can also use the nil-coalescing operator to express this quite succinctly:
let noMiddleName = names.filter { !($0["middleName"] ?? "").isEmpty }
This replaces absent middle names with empty strings, so you can handle either using .isEmpty (and then negate if you want to fetch those with middle names).
You can also use optional chaining and the nil-coalescing operator to express it another way:
let noMiddleName = names.filter { !($0["middleName"]?.isEmpty ?? true) }
$0["middleName"]?.isEmpty will call isEmpty if the value isn’t nil, but returns an optional (because it might have been nil). You then use ?? to substitute true for nil.
This also works fine
names.filter {
if let middleName = $0["middleName"] {
return middleName != ""
}
return false
}
