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Swift, an open source programming language that supports multiple programming paradigms and compilation, was released by Apple in 2014 at the WWDC (Apple developer Conference) for the development of iOS,OS X and watchOS applications.

Once a constant is set, its value cannot be changed while the program is running.

Constants can be any data type such as integer constant, floating point constant, character constant, or string constant. There are also constants for enumerated types:

Constants are similar to variables, except that the value of a constant cannot be changed once it is set, while the value of a variable can be changed at will.

Constant declaration

Constants are declared using the keyword let. The syntax is as follows:

Let constantName = (initial value)

The following is an example of using constants in a simple Swift program:

Import Cocoalet constA = 42print (constA)

The execution results of the above procedures are as follows:

forty-two

Type annotation

When you declare a constant or variable, you can add a type annotation to indicate the type of value to be stored in the constant or variable. If you want to add a type annotation, you need to add a colon and space after the constant or variable name, and then add the type name.

Var constantName:= (optional initial value)

The following is a simple example of the use of type annotations for constants in Swift. It is important to note that when a constant is defined, it must have an initial value:

Import Cocoalet constA = 42print (constA) let constB:Float = 3.14159print (constB)

The execution results of the above procedures are as follows:

423.14159

Constant naming

The naming of constants can consist of letters, numbers, and underscores.

Constants need to start with a letter or an underscore.

Swift is a case-sensitive language, so uppercase and lowercase letters are different.

Constant names can also use simple Unicode characters, as shown in the following example:

Import Cocoalet _ const = "Hello, Swift!" print (_ const) let Hello = "Hello World" print (Hello)

The execution results of the above procedures are as follows:

Hello, Swift! Hello, World.

Constant output

Variables and constants can be output using the print (swift 2 replaces print with println) function.

You can insert constants in a string using parentheses and backslashes, as shown in the following example:

Import Cocoalet name = "this is how Linux should learn" let site = "the official website address of https://www.linuxprobe.com"print("\(name) is:\ (site)")

The execution results of the above procedures are as follows:

This is how Linux should learn from the official website address: https://www.linuxprobe.com thank you for reading! This is the end of this article on "sample Analysis of Swift constants". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it for more people to see!

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