FailableSequence
Swift Sequences are limited in that they don't support Iterators with a throwing next().
There are several use cases for such sequences, for example FileHandles and other data streams can yield an error on each read operation. The FailableSequence module aims to provide support for these use cases.
Swift may in the future have build-in support for failable Sequences. See the discussion on the swift language forums.
Installation
For a Swift Package
Edit the Package.swift file. Add the FailableSequence as a dependency:
let package = Package(
name: " ... ",
products: [ ... ],
dependencies: [
.package(url: "https://github.com/berikv/FailableSequence.git", from: "0.0.2") // here
],
targets: [
.target(
name: " ... ",
dependencies: [
"FailableSequence" // and here
]),
]
)
For .xcodeproj projects
- Open menu File > Add Packages...
- Search for "https://github.com/berikv/FailableSequence.git" and click Add Package.
- Open your project file, select your target in "Targets".
- Open Dependencies
- Click the + sign
- Add FailableSequence
Use the module by importing it in a .swift file:
import FailableSequence
failableSequence(first: 0) { $0 + 1 }
Usage
Create a failable sequence using a first and next().
import FailableSequence
struct DivisionByZero: Error {}
let sequence = failableSequence(first: 10) { element in
if element == 0 { throw DivisionByZero() }
return 1 / element
}
do {
try sequence.forEach { number in
print(number)
}
} catch {
print(error)
}
Create a lazy failable map from another sequence.
let sequence = (0..<4).failableMap { number -> Int in
if (3 - number) == 0 { throw DivisionByZero() }
return 1 / (3 - number)
}
do {
try sequence.forEach { number in
print(number)
}
} catch {
print(error)
}
Create an Array from a FailableSequence.
// Note, if this sequence throws, it would happen on Array init.
let sequence = (0..<3).failableMap { number -> Int in
if (3 - number) == 0 { throw DivisionByZero() }
return 1 / (3 - number)
}
let array = try Array(sequence) // [0, 0, 1]
Note that throwing an error will not end the sequence.
let sequence = (0..<4).failableMap { number -> Int in
if number == 2 { throw DivisionByZero() }
return 1 / (2 - number)
}
let array = Array(sequence.skipOnThrowSequence) // [0, 1, -1]
License
Licensed under MIT. See the license.md
2k Dec 28, 2022
620 Oct 11, 2022
0 Mar 9, 2022
12 Dec 29, 2022
86 Jun 29, 2022
3 Sep 29, 2022
57 Dec 24, 2022
8 Aug 1, 2022
8 Mar 11, 2019
4 Oct 6, 2022
7 Nov 24, 2022
9 Jan 4, 2023
1 Nov 11, 2021
1 Dec 31, 2021
119 Dec 20, 2022
312 Dec 22, 2022
236 Aug 29, 2022
8 Nov 9, 2022