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 without

importing 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:

[objc] view plaincopyprint?

1. // assert mentioned on page 55
2. assert(true)  
3. // countElements mentioned on page 79
4. countElements("foo") == 3
5. // enumerate mentioned on page 94
6. for (i, j) in enumerate(["A", "B"]) {  
7.     // "0:A", "1:B" will be printed
8.     println("\(i):\(j)")  
9. }  
10. // min mentioned on page 246
11. min(8, 2, 3) == 2
12. // print mentioned on page 85
13. print("Hello "
    )  
14. // println mentioned on page 4
15. println("World")  
16. // sort mentioned on page 14
17. for i in sort(["B", "A"]) {  
18.     // "A", "B" will be printed
19.     println(i)  
20. }  

Now on to the most useful undocumented functions …

abs(signedNumber): Returns the absolute value of a given signed number. Trivial but not documented.

[objc] view plaincopyprint?

1. abs(-1) == 1
2. abs(-42) == 42
3. abs(42) == 42

contains(sequence, element): Returns true if a given sequence (such as an array) contains the specified element. [objc] view plaincopyprint?

1. var languages = ["Swift", "Objective-C"]  
2. contains(languages, "Swift") == true
3. contains(languages, "Java") == false
4. 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. [objc] view plaincopyprint?

1. var languages = ["Swift", "Objective-C"]  
2. var oldLanguages = dropFirst(languages)  
3. 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. [objc] view plaincopyprint?

1. var languages = ["Swift", "Objective-C"]  
2. var newLanguages = dropLast(languages)  
3. equal(newLanguages, ["Swift"]) == true

dump(object): Dumps the contents of an object to standard output.

[objc] view plaincopyprint?

1. var languages = ["Swift", "Objective-C"]  
2. dump(languages)  
3. // Prints:
4. // ▿ 2 elements
5. //   - [0]: Swift
6. //   - [1]: Objective-C

equal(sequence1, sequence2): Returns true if sequence1 and sequence2 contain the same elements.

[objc] view plaincopyprint?

1. var languages = ["Swift", "Objective-C"]  
2. equal(languages, ["Swift", "Objective-C"]) == true
3. var oldLanguages = dropFirst(languages)  
4. equal(oldLanguages, ["Objective-C"]) == true

filter(sequence, includeElementClosure): Returns a the elements from sequence that evaluate to true by includeElementClosure. [objc] view plaincopyprint?

1. for i in filter(1...100, { $0 % 10 == 0 }) {  
2.     // 10, 20, 30, ...
3.     println(i)  
4.     assert(contains([10, 20, 30, 40, 50, 60, 70, 80, 90, 100], i))  
5. }  

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. [objc] view plaincopyprint?

1. var languages = ["Swift", "Objective-C"]  
2. find(languages, "Objective-C") == 1
3. find(languages, "Java") == nil
4. find([29, 85, 42, 96, 75], 42) == 2

indices(sequence): Returns the indices (zero indexed) of the elements in the given sequence. [objc] view plaincopy

相關推薦