LazyCollection

A collection containing the same elements as a Base collection, but on which some operations such as map and filter are implemented lazily.

See Also: LazySequenceType, LazyCollection

Inheritance CollectionType, Indexable, LazyCollectionType, LazySequenceType, SequenceType View Protocol Hierarchy →
Associated Types
  • Elements = Base

The type of the underlying collection

  • Index = Base.Index

A type that represents a valid position in the collection.

Valid indices consist of the position of every element and a "past the end" position that's not valid for use as a subscript.

  • Generator = Base.Generator

Type alias inferred.

  • Element = Base.Generator.Element

Type alias inferred.

  • Index = Base.Index

Type alias inferred.

Type alias inferred.
Import
  • import Swift

Initializers

init(_:)

Construct an instance with base as its underlying Collection instance.

Declaration

  • init(_ base: Base)

Instance Variables

var count: Base.Index.Distance

Returns the number of elements.

Complexity: O(1) if Index conforms to RandomAccessIndexType; O(N) otherwise.

Declaration

  • var count: Base.Index.Distance { get }

Declared In

LazyCollection , CollectionType
var elements: Base

The underlying collection

Declaration

  • var elements: Base { get }
var endIndex: Base.Index

The collection's "past the end" position.

endIndex is not a valid argument to subscript, and is always reachable from startIndex by zero or more applications of successor().

Declaration

  • var endIndex: Base.Index { get }
var first: Base.Generator.Element?

Returns the first element of self, or nil if self is empty.

Declaration

  • var first: Base.Generator.Element? { get }

Declared In

LazyCollection , CollectionType
var indices: Range<Base.Index>

Returns the range of valid index values.

The result's endIndex is the same as that of self. Because Range is half-open, iterating the values of the result produces all valid subscript arguments for self, omitting its endIndex.

Declaration

  • var indices: Range<Base.Index> { get }

Declared In

CollectionType
var isEmpty: Bool

Returns true iff self is empty.

Declaration

  • var isEmpty: Bool { get }

Declared In

LazyCollection , CollectionType
var lazy: LazyCollection<Base>

Identical to self.

Declaration

Declared In

LazyCollectionType , LazySequenceType
var startIndex: Base.Index

The position of the first element in a non-empty collection.

In an empty collection, startIndex == endIndex.

Declaration

  • var startIndex: Base.Index { get }

2 inherited items hidden. (Show all)

Subscripts

subscript(_: Base.Index)

Access the element at position.

Requires: position is a valid position in self and position != endIndex.

Declaration

  • subscript(position: Base.Index) -> Base.Generator.Element { get }
subscript(_: Range<Base.Index>)

Returns a collection representing a contiguous sub-range of self's elements.

Complexity: O(1)

Declaration

Instance Methods

func contains(_:)

Returns true iff an element in self satisfies predicate.

Declaration

  • func contains(@noescape predicate: (Base.Generator.Element) throws -> Bool) rethrows -> Bool

Declared In

CollectionType, SequenceType
func dropFirst()

Returns a subsequence containing all but the first element.

Complexity: O(1)

Declaration

Declared In

CollectionType, SequenceType
func dropFirst(_:)

Returns a subsequence containing all but the first n elements.

Requires: n >= 0 Complexity: O(n)

Declaration

Declared In

CollectionType, SequenceType
func dropLast()

Returns a subsequence containing all but the last element.

Requires: self is a finite sequence. Complexity: O(self.count)

Declaration

Declared In

CollectionType, SequenceType
func dropLast(_:)

Returns a subsequence containing all but the last n elements.

Requires: n >= 0 Complexity: O(self.count)

Declaration

Declared In

CollectionType, SequenceType
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: (Base.Generator.Element, Base.Generator.Element) throws -> Bool) rethrows -> Bool

Declared In

CollectionType, SequenceType
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

Declared In

CollectionType, SequenceType
func filter(_:)

Returns the elements of self that satisfy predicate.

Note: The elements of the result are computed on-demand, as the result is used. No buffering storage is allocated and each traversal step invokes predicate on one or more underlying elements.

Declaration

  • func filter(predicate: (Base.Generator.Elements.Generator.Element) -> Bool) -> LazyFilterCollection<Base.Generator.Elements>

Declared In

LazyCollectionType, CollectionType, LazySequenceType, SequenceType
func flatMap<T>(_: (Base.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: (Base.Generator.Element) throws -> T?) rethrows -> [T]

Declared In

CollectionType, SequenceType
func flatMap<S : SequenceType>(_: (Base.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: (Base.Generator.Element) throws -> S) rethrows -> [S.Generator.Element]

Declared In

CollectionType, SequenceType
func flatMap(_:)

Returns the concatenated results of mapping transform over self. Equivalent to 

  • self.map(transform).flatten()

Complexity: O(1)

Declaration

Declared In

LazyCollectionType, LazySequenceType
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: (Base.Generator.Element) throws -> Void) rethrows

Declared In

CollectionType, SequenceType
func generate()

Returns a generator over the elements of this sequence.

Complexity: O(1).

Declaration

  • func generate() -> Base.Generator
func indexOf(_:)

Returns the first index where predicate returns true for the corresponding value, or nil if such value is not found.

Complexity: O(self.count).

Declaration

  • func indexOf(@noescape predicate: (Base.Generator.Element) throws -> Bool) rethrows -> Base.Index?

Declared In

CollectionType
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: (Base.Generator.Element, Base.Generator.Element) throws -> Bool) rethrows -> Bool

Declared In

CollectionType, SequenceType
func map(_:)

Returns a LazyMapCollection over this Collection. The elements of the result are computed lazily, each time they are read, by calling transform function on a base element.

Declaration

  • func map<U>(transform: (Base.Generator.Elements.Generator.Element) -> U) -> LazyMapCollection<Base.Generator.Elements, U>

Declared In

LazyCollectionType, CollectionType, LazySequenceType, SequenceType
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: (Base.Generator.Element, Base.Generator.Element) throws -> Bool) rethrows -> Base.Generator.Element?

Declared In

CollectionType, SequenceType
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: (Base.Generator.Element, Base.Generator.Element) throws -> Bool) rethrows -> Base.Generator.Element?

Declared In

CollectionType, SequenceType
mutating func popFirst()

If !self.isEmpty, remove the first element and return it, otherwise return nil.

Complexity: O(1)

Declaration

  • mutating func popFirst() -> Base.Generator.Element?

Declared In

CollectionType
mutating func popLast()

If !self.isEmpty, remove the last element and return it, otherwise return nil.

Complexity: O(self.count)

Deprecated: it will be removed in Swift 3.

Declaration

  • mutating func popLast() -> Base.Generator.Element?

Declared In

CollectionType
func prefix(_:)

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 Complexity: O(maxLength)

Declaration

Declared In

CollectionType, SequenceType
func prefixThrough(_:)

Returns prefixUpTo(position.successor())

Complexity: O(1)

Declaration

Declared In

CollectionType
func prefixUpTo(_:)

Returns self[startIndex..<end]

Complexity: O(1)

Declaration

Declared In

CollectionType
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, Base.Generator.Element) throws -> T) rethrows -> T

Declared In

CollectionType, SequenceType
mutating func removeFirst()

Remove the element at startIndex and return it.

Complexity: O(1) Requires: !self.isEmpty.

Declaration

  • mutating func removeFirst() -> Base.Generator.Element

Declared In

CollectionType
mutating func removeFirst(_:)

Remove the first n elements.

Complexity: - O(1) if Index conforms to RandomAccessIndexType - O(n) otherwise Requires: n >= 0 && self.count >= n.

Declaration

  • mutating func removeFirst(n: Int)

Declared In

CollectionType
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() -> [Base.Generator.Element]

Declared In

CollectionType, SequenceType
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: (Base.Generator.Element, Base.Generator.Element) -> Bool) -> [Base.Generator.Element]

Declared In

CollectionType, SequenceType
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: (Base.Generator.Element) throws -> Bool) rethrows -> [LazyCollection<Slice<Base>>]

Declared In

CollectionType, SequenceType
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: (Base.Generator.Element, Base.Generator.Element) throws -> Bool) rethrows -> Bool

Declared In

CollectionType, SequenceType
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: maxLength >= 0 Complexity: O(self.count)

Declaration

Declared In

CollectionType, SequenceType
func suffixFrom(_:)

Returns self[start..<endIndex]

Complexity: O(1)

Declaration

Declared In

CollectionType
func underestimateCount()

Returns a value less than or equal to the number of elements in self, nondestructively.

Complexity: O(N).

Declaration

  • func underestimateCount() -> Int

Declared In

LazyCollection, CollectionType, SequenceType

31 inherited items hidden. (Show all)

Conditionally Inherited Items

The initializers, methods, and properties listed below may be available on this type under certain conditions (such as methods that are available on Array when its elements are Equatable) or may not ever be available if that determination is beyond SwiftDoc.org's capabilities. Please open an issue on GitHub if you see something out of place!

Where Elements == Self

var elements: LazyCollection<Base>

Identical to self.

Declaration

Declared In

LazyCollectionType , LazySequenceType

1 inherited item hidden. (Show all)

Where Elements.Generator.Element == Generator.Element, Generator.Element : SequenceType

func flatten()

A concatenation of the elements of self.

Declaration

Declared In

LazySequenceType

1 inherited item hidden. (Show all)

Where Elements.Index : BidirectionalIndexType

func flatMap(_:)

Returns the concatenated results of mapping transform over self. Equivalent to 

  • self.map(transform).flatten()

Complexity: O(1)

Declaration

Declared In

LazyCollectionType

1 inherited item hidden. (Show all)

Where Generator.Element : CollectionType

func flatten()

A concatenation of the elements of self.

Declaration

Declared In

CollectionType

1 inherited item hidden. (Show all)

Where Generator.Element : CollectionType, Elements.Generator.Element : CollectionType, Generator.Element == Elements.Generator.Element

func flatten()

A concatenation of the elements of self.

Declaration

Declared In

LazyCollectionType

1 inherited item hidden. (Show all)

Where Generator.Element : CollectionType, Index : BidirectionalIndexType, Generator.Element.Index : BidirectionalIndexType

func flatten()

A concatenation of the elements of self.

Declaration

Declared In

CollectionType

1 inherited item hidden. (Show all)

Where Generator.Element : CollectionType, Index : BidirectionalIndexType, Generator.Element.Index : BidirectionalIndexType, Elements.Generator.Element : CollectionType, Elements.Index : BidirectionalIndexType, Elements.Generator.Element.Index : BidirectionalIndexType, Generator.Element == Elements.Generator.Element

func flatten()

A concatenation of the elements of self.

Declaration

Declared In

LazyCollectionType

1 inherited item hidden. (Show all)

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

Declared In

CollectionType, SequenceType
func maxElement()

Returns the maximum element in self or nil if the sequence is empty.

Complexity: O(elements.count).

Declaration

  • func maxElement() -> Base.Generator.Element?

Declared In

CollectionType, SequenceType
func minElement()

Returns the minimum element in self or nil if the sequence is empty.

Complexity: O(elements.count).

Declaration

  • func minElement() -> Base.Generator.Element?

Declared In

CollectionType, SequenceType
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() -> [Base.Generator.Element]

Declared In

CollectionType, SequenceType

4 inherited items hidden. (Show all)

Where Generator.Element : Equatable

func contains(_:)

Returns true iff element is in self.

Declaration

  • func contains(element: Base.Generator.Element) -> Bool

Declared In

CollectionType, SequenceType
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

Declared In

CollectionType, SequenceType
func indexOf(_:)

Returns the first index where value appears in self or nil if value is not found.

Complexity: O(self.count).

Declaration

  • func indexOf(element: Base.Generator.Element) -> Base.Index?

Declared In

CollectionType
func split(_:maxSplit:allowEmptySlices:)

Returns the maximal SubSequences of self, in order, around a separator element.

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: Base.Generator.Element, maxSplit: Int = default, allowEmptySlices: Bool = default) -> [LazyCollection<Slice<Base>>]

Declared In

CollectionType, SequenceType
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

Declared In

CollectionType, SequenceType

5 inherited items hidden. (Show all)

Where Generator.Element : SequenceType

func flatten()

A concatenation of the elements of self.

Declaration

Declared In

CollectionType, SequenceType
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

Declared In

CollectionType, SequenceType

2 inherited items hidden. (Show all)

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

Declared In

CollectionType, SequenceType

1 inherited item hidden. (Show all)

Where Index : BidirectionalIndexType

var last: Base.Generator.Element?

Declaration

  • var last: Base.Generator.Element? { get }

Declared In

CollectionType
func dropLast(_:)

Returns a subsequence containing all but the last n elements.

Requires: n >= 0 Complexity: O(n)

Declaration

Declared In

CollectionType
func reverse()

Returns the elements of self in reverse order.

Complexity: O(1)

Declaration

Declared In

CollectionType
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: maxLength >= 0 Complexity: O(maxLength)

Declaration

Declared In

CollectionType

4 inherited items hidden. (Show all)

Where Index : BidirectionalIndexType, Elements.Index : BidirectionalIndexType

func reverse()

Returns the elements of self in reverse order.

Complexity: O(1)

Declaration

Declared In

LazyCollectionType

1 inherited item hidden. (Show all)

Where Index : RandomAccessIndexType

func reverse()

Returns the elements of self in reverse order.

Complexity: O(1)

Declaration

Declared In

CollectionType

1 inherited item hidden. (Show all)

Where Index : RandomAccessIndexType, Elements.Index : RandomAccessIndexType

func reverse()

Returns the elements of self in reverse order.

Complexity: O(1)

Declaration

Declared In

LazyCollectionType

1 inherited item hidden. (Show all)

Where SubSequence == Self, Index : BidirectionalIndexType

mutating func popLast()

If !self.isEmpty, remove the last element and return it, otherwise return nil.

Complexity: O(1)

Declaration

  • mutating func popLast() -> Base.Generator.Element?

Declared In

CollectionType
mutating func removeLast()

Remove an element from the end.

Complexity: O(1) Requires: !self.isEmpty

Declaration

  • mutating func removeLast() -> Base.Generator.Element

Declared In

CollectionType
mutating func removeLast(_:)

Remove the last n elements.

Complexity: - O(1) if Index conforms to RandomAccessIndexType - O(n) otherwise Requires: n >= 0 && self.count >= n.

Declaration

  • mutating func removeLast(n: Int)

Declared In

CollectionType

3 inherited items hidden. (Show all)