9.16. Swift cycle

发布时间 :2023-12-08 01:10:05 UTC      

Sometimes, we may need to execute the same piece of code multiple times. In general, statements are executed sequentially: the first statement in the function is executed first, then the second statement, and so on.

Programming languages provide a variety of control structures for more complex execution paths.

Loop statements allow us to execute a statement or group of statements multiple times. Here is a flowchart of loop statements in most programming languages:

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9.16.1. Cycle type #

The Swift language provides the following loop types. Click the link to viewa detailed description of each type:

Cycle type

Description

For-in

Iterate through all the elements in a set, such as intervals represented by numbers, elements in an array, characters in a string.

For cycle

Used to repeat a series of statements until specific conditions are met, usually by increasing the value of the counter after each loop is completed.

While cycle

Run a series of statements that, if the condition is true, run repeatedly until the condition becomes false.

Repeat…while cycle

A similar while statement differs from a block of code that executes a loop before determining a loop condition.

9.16.2. Loop control statement #

Loop control statements change the order in which your code is executed, through which you can jump the code. Swift has the following loop control statements:

Control statement

Description

Continue statement

Tell a loop body to stop this loop iteration immediately and restart the next loop iteration.

Break statement

Interrupts the current loop.

Fallthrough statement

If you continue to execute the following case after a case has been executed, you need to use the fallthrough keyword.

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.