iOS Development Swift Chapter-(v) Tuple types

iOS Development Swift Chapter-(v) Tuple types

I. Introduction to the type of meta-group

1. What is a tuple type

A tuple type consists of n arbitrary types of data (n >= 0), and the data that makes up the tuple type can be called an "element"

Example:

Let position = (x:10.5, y:20) //position has 2 elements, X, Y is the name of the element

Let man = (name: "Jack") //person only name one element

Let data = () //Empty tuple

2. Access to elements

var position = (x:10.5, y:20)

(1) with element name

Let value = position.x //value

POSITION.Y = //Set Value

(2) position with element

var value = position.0 //equivalent to var value = postion.x

Position.1 = //equivalent to POSTION.Y =

code example:

Note : If you use let to define a tuple, then it is a constant and you cannot modify its elements

Let point = (X:10, y:20)

Point.x = 30

The 2nd line of code will error

code example:

3. Meta-Set output

You can output an entire tuple to see the values of all the elements

var point = (x:10.5, y:20)

Point.x = 30

Point.1 = 50

println (Point)

The output is:(30.0, +)

Second, the use of details

(1) Element name can be omitted

Let position = (10, 20)

Let person = ("Jack")

(2) The type of the element can be specified explicitly

var person: (Int, String) = (all, "Rose")

The No. 0 element of person can only be of type int, 1th element can only be string type

Note : You cannot add an element name when you explicitly specify an element type

Therefore, the following statement is incorrect

var person: (Int, String) = (age:23, name: "Rose")

(3) can receive tuple data with multiple variables

var (x, y) = (ten, +) //x is 10,y

var point = (x, y) //point consists of 2 elements, respectively, 10 and

(4) You can assign elements to multiple variables individually

var point = (10, 20)

var (x, y) = point

X is 10,y is 20

(5) You can use the underscore _ to ignore the value of an element and to remove the value of another element

var person = ("Jack")

var (_, name) = person

The content of name is "Jack", and element 20 in person is ignored