flowapp / SwiftSortDescriptor

SwiftSortDescriptor

Example

To run the example project, clone the repo, and run pod install from the Example directory first.

Usage

struct Item {
    let a: Int
    let b: Int
    let c: String?
}

let items = [
  Item(a: 1, b: nil),
  Item(a: 1, b: "1"),
  Item(a: 1, b: "2"),
  Item(a: 2, b: nil),
  Item(a: 2, b: "1"),
  Item(a: 2, b: "2")
]


// create a SortDescriptor which sorts
// In the closure return the "keyPath" on which you want to sort
let aDescriptor = SortDescriptor<Item>(ascending: false) { $0.a }

// by default SortDescriptors sort ascending
let bDescriptor = SortDescriptor<Item>() { $0.b }

let sorted = items.sorted(descriptors: [aDescriptor, bDescriptor])

/*sorted now contains:
a: 2, b: nil,
a: 2, b: "1",
a: 2, b: "2"
a: 1, c: nil,
a: 1, b: "1",
a: 1, b: "2",
*/

Sorting on Optional Properties

When evaluating Optionals the following rule is applied:

.none < .some(_) == true

Most of the time this is the desired behaviour.

To get around this i recommend using a second SortDescriptor like this:

Example

// Items should be sorted in the following order:
// - b descending items which are nil should appear first
// - a ascending


let bDescriptor = SortDescriptor<Item>() { $0.b }
let aDescriptor = SortDescriptor<Item>(ascending: false) { $0.a }

var bExistsDescriptor = SortDescriptor<Item>(ascending: true) { $0.b != nil }

// This can be confusing
// For this purpose a helper method can be used

bExistsDescriptor = SortDescriptor<Item>.exists(nilFirst: true) { $0.b }


// or create from an existing SortDescriptor

bExistsDescriptor = bDescriptor.existsDescriptor


let sorted = items.sorted(descriptors: [aDescriptor, bDescriptor])

/*sorted now contains:
a: 2, b: nil,
a: 1, c: nil,
a: 2, b: "1",
a: 1, b: "1",
a: 2, b: "2"
a: 1, b: "2",
*/

Requirements

Installation

SwiftSortDescriptor is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod "SwiftSortDescriptor"

Author

Simon Anreiter, [e-mail]

License

SwiftSortDescriptor is available under the MIT license. See the LICENSE file for more info.