Key_path_Map_Filter.swift

struct Size {
    var width: Int
    let height: Int
}

enum Material: String {
    case wood
    case iron
}

struct Table {
    var size: Size
    let material: Material
}

extension Table {
    var isWood: Bool {
        return material == .wood
    }
}

let tables: [Table] = [
    .init(
        size: .init(width: 150, height: 10),
        material: .iron
    ),
    .init(
        size: .init(width: 200, height: 10),
        material: .iron
    ),
    .init(
        size: .init(width: 100, height: 10),
        material: .wood
    )
]

// Mapping
let tableMaterials = tables.map(\.material)
// Filtering
let woodTables = tables.filter(\.isWood)