Swift Language Arrays Grouping Array values
Example
If we have a struct like this
struct Box {
let name: String
let thingsInside: Int
}
and an array of Box(es)
let boxes = [
Box(name: "Box 0", thingsInside: 1),
Box(name: "Box 1", thingsInside: 2),
Box(name: "Box 2", thingsInside: 3),
Box(name: "Box 3", thingsInside: 1),
Box(name: "Box 4", thingsInside: 2),
Box(name: "Box 5", thingsInside: 3),
Box(name: "Box 6", thingsInside: 1)
]
we can group the boxes by the thingsInside property in order to get a Dictionary where the key is the number of things and the value is an array of boxes.
let grouped = boxes.reduce([Int:[Box]]()) { (res, box) -> [Int:[Box]] in
var res = res
res[box.thingsInside] = (res[box.thingsInside] ?? []) + [box]
return res
}
Now grouped is a [Int:[Box]] and has the following content
[
2: [Box(name: "Box 1", thingsInside: 2), Box(name: "Box 4", thingsInside: 2)],
3: [Box(name: "Box 2", thingsInside: 3), Box(name: "Box 5", thingsInside: 3)],
1: [Box(name: "Box 0", thingsInside: 1), Box(name: "Box 3", thingsInside: 1), Box(name: "Box 6", thingsInside: 1)]
]
