protocol SequenceType A type that can be iterated with a for...in loop. SequenceType makes no requirement on conforming types regarding whether they will be destructively "consumed" by iteration. To ensure non-destructive iteration, constrain your sequence to CollectionType. As a consequence, it is not possible to run multiple for loops on a sequence to "resume" iteration: for element in sequence { if ... some condition { break } } for element in sequence { // Not guaranteed to continue from the next element. } SequenceType makes no requirement about the behavior in that case. It is not correct to assume that a sequence will either be "consumable" and will resume iteration, or that a sequence is a collection and will restart iteration from the first element. A conforming sequence that is not a collection is allowed to produce an arbitrary sequence of elements from the second generator. Inheritance View Protocol Hierarchy → Associated Types Generator : GeneratorType A type that provides the sequence's iteration interface and encapsulates its iteration state. SubSequence A type that represents a subsequence of some of the elements. Import import Swift Instance Methods func dropFirst(_:) Required Returns a subsequence containing all but the first n elements. Requires: n >= 0 Complexity: O(n) Declaration func dropFirst(n: Int) -> Self.SubSequence func dropLast(_:) Required Returns a subsequence containing all but the last n elements. Requires: self is a finite sequence. Requires: n >= 0 Complexity: O(self.count) Declaration func dropLast(n: Int) -> Self.SubSequence func filter(_:) Returns an Array containing the elements of self, in order, that satisfy the predicate includeElement. Declaration func filter(@noescape includeElement: (Self.Generator.Element) throws -> Bool) rethrows -> [Self.Generator.Element] func forEach(_:) Call body on each element in self in the same order as a for-in loop. sequence.forEach { // body code } is similar to: for element in sequence { // body code } Note: You cannot use the break or continue statement to exit the current call of the body closure or skip subsequent calls. Note: Using the return statement in the body closure will only exit from the current call to body, not any outer scope, and won't skip subsequent calls. Complexity: O(self.count) Declaration func forEach(@noescape body: (Self.Generator.Element) throws -> Void) rethrows func generate() Required Returns a generator over the elements of this sequence. Complexity: O(1). Declaration func generate() -> Self.Generator func map(_:) Returns an Array containing the results of mapping transform over self. Complexity: O(N). Declaration func map<T>(@noescape transform: (Self.Generator.Element) throws -> T) rethrows -> [T] func prefix(_:) Required Returns a subsequence, up to maxLength in length, containing the initial elements. If maxLength exceeds self.count, the result contains all the elements of self. Requires: maxLength >= 0 Declaration func prefix(maxLength: Int) -> Self.SubSequence func split(_:allowEmptySlices:isSeparator:) Returns the maximal SubSequences of self, in order, that don't contain elements satisfying the predicate isSeparator. maxSplit: The maximum number of SubSequences to return, minus 1. If maxSplit + 1 SubSequences are returned, the last one is a suffix of self containing the remaining elements. The default value is Int.max. allowEmptySubsequences: If true, an empty SubSequence is produced in the result for each pair of consecutive elements satisfying isSeparator. The default value is false. Requires: maxSplit >= 0 Declaration func split(maxSplit: Int, allowEmptySlices: Bool, @noescape isSeparator: (Self.Generator.Element) throws -> Bool) rethrows -> [Self.SubSequence] func suffix(_:) Returns a slice, up to maxLength in length, containing the final elements of s. If maxLength exceeds s.count, the result contains all the elements of s. Requires: self is a finite sequence. Requires: maxLength >= 0 Declaration func suffix(maxLength: Int) -> Self.SubSequence func underestimateCount() Returns a value less than or equal to the number of elements in self, nondestructively. Complexity: O(N). Declaration func underestimateCount() -> Int Default Implementations var lazy: LazySequence<Self> A sequence containing the same elements as a Base sequence, but on which some operations such as map and filter are implemented lazily. See Also: LazySequenceType, LazySequence Declaration var lazy: LazySequence<Self> { get } func contains(_:) Returns true iff an element in self satisfies predicate. Declaration func contains(@noescape predicate: (Self.Generator.Element) throws -> Bool) rethrows -> Bool func dropFirst() Returns a subsequence containing all but the first element. Complexity: O(1) Declaration func dropFirst() -> Self.SubSequence func dropLast() Returns a subsequence containing all but the last element. Requires: self is a finite sequence. Complexity: O(self.count) Declaration func dropLast() -> Self.SubSequence func elementsEqual(_:isEquivalent:) Returns true iff self and other contain equivalent elements, using isEquivalent as the equivalence test. Requires: isEquivalent is an equivalence relation. Declaration func elementsEqual<OtherSequence : SequenceType where OtherSequence.Generator.Element == Generator.Element>(other: OtherSequence, @noescape isEquivalent: (Self.Generator.Element, Self.Generator.Element) throws -> Bool) rethrows -> Bool func enumerate() Returns a lazy SequenceType containing pairs (n, x), where ns are consecutive Ints starting at zero, and xs are the elements of base: > for (n, c) in "Swift".characters.enumerate() { print("\(n): '\(c)'") } 0: 'S' 1: 'w' 2: 'i' 3: 'f' 4: 't' Declaration func enumerate() -> EnumerateSequence<Self> func filter(_:) Returns an Array containing the elements of self, in order, that satisfy the predicate includeElement. Declaration func filter(@noescape includeElement: (Self.Generator.Element) throws -> Bool) rethrows -> [Self.Generator.Element] func flatMap<T>(_: (Self.Generator.Element) throws -> T?) Returns an Array containing the non-nil results of mapping transform over self. Complexity: O(M + N), where M is the length of self and N is the length of the result. Declaration func flatMap<T>(@noescape transform: (Self.Generator.Element) throws -> T?) rethrows -> [T] func flatMap<S : SequenceType>(_: (Self.Generator.Element) throws -> S) Returns an Array containing the concatenated results of mapping transform over self. s.flatMap(transform) is equivalent to Array(s.map(transform).flatten()) Complexity: O(M + N), where M is the length of self and N is the length of the result. Declaration func flatMap<S : SequenceType>(transform: (Self.Generator.Element) throws -> S) rethrows -> [S.Generator.Element] func forEach(_:) Call body on each element in self in the same order as a for-in loop. sequence.forEach { // body code } is similar to: for element in sequence { // body code } Note: You cannot use the break or continue statement to exit the current call of the body closure or skip subsequent calls. Note: Using the return statement in the body closure will only exit from the current call to body, not any outer scope, and won't skip subsequent calls. Complexity: O(self.count) Declaration func forEach(@noescape body: (Self.Generator.Element) throws -> Void) rethrows func lexicographicalCompare(_:isOrderedBefore:) Returns true iff self precedes other in a lexicographical ("dictionary") ordering, using isOrderedBefore as the comparison between elements. Note: This method implements the mathematical notion of lexicographical ordering, which has no connection to Unicode. If you are sorting strings to present to the end-user, you should use String APIs that perform localized comparison. Requires: isOrderedBefore is a strict weak ordering over the elements of self and other. Declaration func lexicographicalCompare<OtherSequence : SequenceType where OtherSequence.Generator.Element == Generator.Element>(other: OtherSequence, @noescape isOrderedBefore: (Self.Generator.Element, Self.Generator.Element) throws -> Bool) rethrows -> Bool func map(_:) Returns an Array containing the results of mapping transform over self. Complexity: O(N). Declaration func map<T>(@noescape transform: (Self.Generator.Element) throws -> T) rethrows -> [T] func maxElement(_:) Returns the maximum element in self or nil if the sequence is empty. Complexity: O(elements.count). Requires: isOrderedBefore is a strict weak ordering over self. Declaration func maxElement(@noescape isOrderedBefore: (Self.Generator.Element, Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? func minElement(_:) Returns the minimum element in self or nil if the sequence is empty. Complexity: O(elements.count). Requires: isOrderedBefore is a strict weak ordering over self. Declaration func minElement(@noescape isOrderedBefore: (Self.Generator.Element, Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? func reduce(_:combine:) Returns the result of repeatedly calling combine with an accumulated value initialized to initial and each element of self, in turn, i.e. return combine(combine(...combine(combine(initial, self[0]), self[1]),...self[count-2]), self[count-1]). Declaration func reduce<T>(initial: T, @noescape combine: (T, Self.Generator.Element) throws -> T) rethrows -> T func reverse() Returns an Array containing the elements of self in reverse order. Complexity: O(N), where N is the length of self. Declaration func reverse() -> [Self.Generator.Element] func sort(_:) Returns an Array containing the sorted elements of source according to isOrderedBefore. The sorting algorithm is not stable (can change the relative order of elements for which isOrderedBefore does not establish an order). Requires: isOrderedBefore is a strict weak ordering over the elements in self. Declaration func sort(@noescape isOrderedBefore: (Self.Generator.Element, Self.Generator.Element) -> Bool) -> [Self.Generator.Element] func split(_:allowEmptySlices:isSeparator:) Returns the maximal SubSequences of self, in order, that don't contain elements satisfying the predicate isSeparator. maxSplit: The maximum number of SubSequences to return, minus 1. If maxSplit + 1 SubSequences are returned, the last one is a suffix of self containing the remaining elements. The default value is Int.max. allowEmptySubsequences: If true, an empty SubSequence is produced in the result for each pair of consecutive elements satisfying isSeparator. The default value is false. Requires: maxSplit >= 0 Declaration func split(maxSplit: Int = default, allowEmptySlices: Bool = default, @noescape isSeparator: (Self.Generator.Element) throws -> Bool) rethrows -> [AnySequence<Self.Generator.Element>] func startsWith(_:isEquivalent:) Returns true iff self begins with elements equivalent to those of other, using isEquivalent as the equivalence test. Returns true if other is empty. Requires: isEquivalent is an equivalence relation. Declaration func startsWith<OtherSequence : SequenceType where OtherSequence.Generator.Element == Generator.Element>(other: OtherSequence, @noescape isEquivalent: (Self.Generator.Element, Self.Generator.Element) throws -> Bool) rethrows -> Bool func suffix(_:) Declaration func suffix(maxLength: Int) -> AnySequence<Self.Generator.Element> func underestimateCount() Returns a value less than or equal to the number of elements in self, nondestructively. Complexity: O(N). Declaration func underestimateCount() -> Int Where Generator == Self, Self : GeneratorType func generate() Declaration func generate() -> Self Where Generator.Element : Comparable func lexicographicalCompare(_:) Returns true iff self precedes other in a lexicographical ("dictionary") ordering, using "<" as the comparison between elements. Note: This method implements the mathematical notion of lexicographical ordering, which has no connection to Unicode. If you are sorting strings to present to the end-user, you should use String APIs that perform localized comparison. Declaration func lexicographicalCompare<OtherSequence : SequenceType where OtherSequence.Generator.Element == Generator.Element>(other: OtherSequence) -> Bool func maxElement() Returns the maximum element in self or nil if the sequence is empty. Complexity: O(elements.count). Declaration func maxElement() -> Self.Generator.Element? func minElement() Returns the minimum element in self or nil if the sequence is empty. Complexity: O(elements.count). Declaration func minElement() -> Self.Generator.Element? func sort() Returns an Array containing the sorted elements of source. The sorting algorithm is not stable (can change the relative order of elements that compare equal). Requires: The less-than operator (func <) defined in the Comparable conformance is a strict weak ordering over the elements in self. Declaration func sort() -> [Self.Generator.Element] Where Generator.Element : Equatable func contains(_:) Returns true iff element is in self. Declaration func contains(element: Self.Generator.Element) -> Bool func elementsEqual(_:) Returns true iff self and other contain the same elements in the same order. Declaration func elementsEqual<OtherSequence : SequenceType where OtherSequence.Generator.Element == Generator.Element>(other: OtherSequence) -> Bool func split(_:maxSplit:allowEmptySlices:) Returns the maximal SubSequences of self, in order, around elements equatable to separator. maxSplit: The maximum number of SubSequences to return, minus 1. If maxSplit + 1 SubSequences are returned, the last one is a suffix of self containing the remaining elements. The default value is Int.max. allowEmptySubsequences: If true, an empty SubSequence is produced in the result for each pair of consecutive elements satisfying isSeparator. The default value is false. Requires: maxSplit >= 0 Declaration func split(separator: Self.Generator.Element, maxSplit: Int = default, allowEmptySlices: Bool = default) -> [AnySequence<Self.Generator.Element>] func startsWith(_:) Returns true iff the initial elements of self are equal to prefix. Returns true if other is empty. Declaration func startsWith<OtherSequence : SequenceType where OtherSequence.Generator.Element == Generator.Element>(other: OtherSequence) -> Bool Where Generator.Element : SequenceType func flatten() A concatenation of the elements of self. Declaration func flatten() -> FlattenSequence<Self> func joinWithSeparator(_:) Returns a view, whose elements are the result of interposing a given separator between the elements of the sequence self. For example, [[1, 2, 3], [4, 5, 6], [7, 8, 9]].joinWithSeparator([-1, -2]) yields [1, 2, 3, -1, -2, 4, 5, 6, -1, -2, 7, 8, 9]. Declaration func joinWithSeparator<Separator : SequenceType where Separator.Generator.Element == Generator.Element.Generator.Element>(separator: Separator) -> JoinSequence<Self> Where Generator.Element == String func joinWithSeparator(_:) Interpose the separator between elements of self, then concatenate the result. For example: ["foo", "bar", "baz"].joinWithSeparator("-|-") // "foo-|-bar-|-baz" Declaration func joinWithSeparator(separator: String) -> String Where Self : _SequenceWrapperType, Generator == Base.Generator func filter(_:) Declaration func filter(@noescape includeElement: (Self.Generator.Element) throws -> Bool) rethrows -> [Self.Generator.Element] func generate() Returns a generator over the elements of this sequence. Complexity: O(1). Declaration func generate() -> Self.Generator func map(_:) Declaration func map<T>(@noescape transform: (Self.Generator.Element) throws -> T) rethrows -> [T] func underestimateCount() Declaration func underestimateCount() -> Int Where SubSequence : SequenceType, SubSequence.Generator.Element == Generator.Element, SubSequence.SubSequence == SubSequence func dropFirst(_:) Returns a subsequence containing all but the first n elements. Requires: n >= 0 Complexity: O(n) Declaration func dropFirst(n: Int) -> AnySequence<Self.Generator.Element> func dropLast(_:) Returns a subsequence containing all but the last n elements. Requires: self is a finite collection. Requires: n >= 0 Complexity: O(self.count) Declaration func dropLast(n: Int) -> AnySequence<Self.Generator.Element> func prefix(_:) Declaration func prefix(maxLength: Int) -> AnySequence<Self.Generator.Element>