Swift has 74 built-in functions but only seven of them are documented in the Swift book (“The Swift Programming Language”). The rest remain undocumented.
This article lists all built-in Swift functions – both documented and undocumented ones. The definition used for “built-in function” used in this article is a function available in Swift withoutimporting any modules (such as Foundation, etc.) or referencing any classes.
Let’s start with the seven documented built-in functions mentioned in the Swift book along with the page number on which the function was first mentioned:
// assert mentioned on page 55
assert(true)
// countElements mentioned on page 79
countElements("foo") == 3
// enumerate mentioned on page 94
for (i, j) in enumerate(["A", "B"]) {
// "0:A", "1:B" will be printed
println("\(i):\(j)")
}
// min mentioned on page 246
min(8, 2, 3) == 2
// print mentioned on page 85
print("Hello ")
// println mentioned on page 4
println("World")
// sort mentioned on page 14
for i in sort(["B", "A"]) {
// "A", "B" will be printed
println(i)
}
Now on to the most useful undocumented functions …
abs(signedNumber): Returns the absolute value of a given signed number. Trivial but not documented.
abs(-1) == 1 abs(-42) == 42 abs(42) == 42
contains(sequence, element) : Returns true if a given sequence (such as an array) contains the specified element.
var languages = ["Swift", "Objective-C"] contains(languages, "Swift") == true contains(languages, "Java") == false contains([29, 85, 42, 96, 75], 42) == true
dropFirst(sequence) : Returns a new sequence (such as an array) without the first element of the sequence.
var languages = ["Swift", "Objective-C"] var oldLanguages = dropFirst(languages) equal(oldLanguages, ["Objective-C"]) == true
dropLast(sequence) : Returns a new sequence (such as an array) without the last element of the sequence passed as argument to the function.
var languages = ["Swift", "Objective-C"] var newLanguages = dropLast(languages) equal(newLanguages, ["Swift"]) == true
dump(object): Dumps the contents of an object to standard output.
var languages = ["Swift", "Objective-C"] dump(languages) // Prints: // ▿ 2 elements // - [0]: Swift // - [1]: Objective-C
equal(sequence1, sequence2): Returns true if sequence1 and sequence2 contain the same elements.
var languages = ["Swift", "Objective-C"] equal(languages, ["Swift", "Objective-C"]) == true var oldLanguages = dropFirst(languages) equal(oldLanguages, ["Objective-C"]) == true
for i in filter(1...100, { $0 % 10 == 0 }) {
// 10, 20, 30, ...
println(i)
assert(contains([10, 20, 30, 40, 50, 60, 70, 80, 90, 100], i))
}
find(sequence, element) : Return the index of a specified element in the given sequence. Or nil if the element is not found in the sequence.
var languages = ["Swift", "Objective-C"] find(languages, "Objective-C") == 1 find(languages, "Java") == nil find([29, 85, 42, 96, 75], 42) == 2
indices(sequence) : Returns the indices (zero indexed) of the elements in the given sequence.
equal(indices([29, 85, 42]), [0, 1, 2])
for i in indices([29, 85, 42]) {
// 0, 1, 2
println(i)
}
join(":", ["A", "B", "C"]) == "A:B:C"
var languages = ["Swift", "Objective-C"]
join("/", languages) == "Swift/Objective-C"
map(sequence, transformClosure): Returns a new sequence with the transformClosure applied to all elements in the supplied sequence.
equal(map(1...3, { $0 * 5 }), [5, 10, 15])
for i in map(1...10, { $0 * 10 }) {
// 10, 20, 30, ...
println(i)
assert(contains([10, 20, 30, 40, 50, 60, 70, 80, 90, 100], i))
}
max(comparable1, comparable2, etc.): Returns the largest of the arguments given to the function.
max(0, 1) == 1 max(8, 2, 3) == 8
maxElement(sequence): Returns the largest element in a supplied sequence of comparable elements.
maxElement(1...10) == 10 var languages = ["Swift", "Objective-C"] maxElement(languages) == "Swift"
minElements(sequence) : Returns the smallest element in a supplied sequence of comparable elements.
minElement(1...10) == 1 var languages = ["Swift", "Objective-C"] minElement(languages) == "Objective-C"
reduce(sequence, initial, combineClosure): Recursively reduce the elements in sequence into one value by running the combineClosure on them with starting value of initial.
var languages = ["Swift", "Objective-C"]
reduce(languages, "", { $0 + $1 }) == "SwiftObjective-C"
reduce([10, 20, 5], 1, { $0 * $1 }) == 1000
reverse(sequence): Returns the elements of the given sequence reversed.
equal(reverse([1, 2, 3]), [3, 2, 1])
for i in reverse([1, 2, 3]) {
// 3, 2, 1
println(i)
}
startsWith(sequence1, sequence2): Return true if the starting elements sequence1 are equal to the of sequence2.
startsWith("foobar", "foo") == true
startsWith(10..100, 10..15) == true
var languages = ["Swift", "Objective-C"]
startsWith(languages, ["Swift"]) == true
Below is the full list of all 74 built-in functions in Swift. The functions covered above are the ones I think are useful on a day-to-day basis, but perhaps I’ve missed some functions from the list below that deserves coverage. If so, let me know in the comments section and please include a short code snippet to show how to use the function.
Happy Swifting!
abs(...) advance(...) alignof(...) alignofValue(...) assert(...) bridgeFromObjectiveC(...) bridgeFromObjectiveCUnconditional(...) bridgeToObjectiveC(...) bridgeToObjectiveCUnconditional(...) c_malloc_size(...) c_memcpy(...) c_putchar(...) contains(...) count(...) countElements(...) countLeadingZeros(...) debugPrint(...) debugPrintln(...) distance(...) dropFirst(...) dropLast(...) dump(...) encodeBitsAsWords(...) enumerate(...) equal(...) filter(...) find(...) getBridgedObjectiveCType(...) getVaList(...) indices(...) insertionSort(...) isBridgedToObjectiveC(...) isBridgedVerbatimToObjectiveC(...) isUniquelyReferenced(...) join(...) lexicographicalCompare(...) map(...) max(...) maxElement(...) min(...) minElement(...) numericCast(...) partition(...) posix_read(...) posix_write(...) print(...) println(...) quickSort(...) reduce(...) reflect(...) reinterpretCast(...) reverse(...) roundUpToAlignment(...) sizeof(...) sizeofValue(...) sort(...) split(...) startsWith(...) strideof(...) strideofValue(...) swap(...) swift_MagicMirrorData_summaryImpl(...) swift_bufferAllocate(...) swift_keepAlive(...) toString(...) transcode(...) underestimateCount(...) unsafeReflect(...) withExtendedLifetime(...) withObjectAtPlusZero(...) withUnsafePointer(...) withUnsafePointerToObject(...) withUnsafePointers(...) withVaList(...)
original article： Here