9.17. Swift for-in cycle

发布时间 :2023-12-08 01:10:06 UTC      

Swift for-in loops are used to traverse all the elements in a collection, such as intervals represented by numbers, elements in an array, and characters in a string.

9.17.1. Grammar #

Swift for-in the syntax format of the loop is as follows:

for index in var {
   loop body
}

Flow chart:

Image0

9.17.2. Example 1 #

import Cocoa

for index in 1...5 {
    print("\(index) multiplying by 5 is:\(index * 5)")
}

The element used for traversal in the example is a numerical range from 1 to 5 represented by the closed interval operator (…).

The output of the above program execution is as follows:

Multiplying 1 by 5 is: 5
Multiplying 2 by 5 is: 10
Multiplying 3 by 5 is: 15
Multiplying 4 by 5 is: 20
Multiplying 5 by 5 is: 25

9.17.3. Example 2 #

import Cocoa

var someInts:[Int] = [10, 20, 30]

for index in someInts {
   print( "The value of index is \(index)")
}

The output of the above program execution is as follows:

The value of index is 10
The value of index is 20
The value of index is 30

Principles, Technologies, and Methods of Geographic Information Systems  102

In recent years, Geographic Information Systems (GIS) have undergone rapid development in both theoretical and practical dimensions. GIS has been widely applied for modeling and decision-making support across various fields such as urban management, regional planning, and environmental remediation, establishing geographic information as a vital component of the information era. The introduction of the “Digital Earth” concept has further accelerated the advancement of GIS, which serves as its technical foundation. Concurrently, scholars have been dedicated to theoretical research in areas like spatial cognition, spatial data uncertainty, and the formalization of spatial relationships. This reflects the dual nature of GIS as both an applied technology and an academic discipline, with the two aspects forming a mutually reinforcing cycle of progress.