{"id":97,"date":"2024-08-31T10:47:45","date_gmt":"2024-08-31T03:47:45","guid":{"rendered":"https:\/\/gotutorial.org\/?page_id=97"},"modified":"2024-09-23T09:38:07","modified_gmt":"2024-09-23T02:38:07","slug":"go-constants","status":"publish","type":"page","link":"https:\/\/www.gotutorial.org\/go-tutorial\/go-constants\/","title":{"rendered":"Go Constants"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you will learn how to use Go constants to represent values that cannot be changed throughout the program.<\/p>\n\n\n\n

Constants are identifiers whose values cannot be changed during the execution of the program. Constants can be useful for values that are known at compile time and should remain unchanged.<\/p>\n\n\n\n

In Go, you can define constants for numbers, strings, and booleans. Constant values can be literals or compile-time functions of other constants.<\/p>\n\n\n\n

Declaring constants<\/h2>\n\n\n\n

To declare constants in Go, you use the const<\/code> keyword. Unlike a variable<\/a>, you need to declare and assign a value to a constant immediately:<\/p>\n\n\n

const<\/span> constantName type<\/span> = value<\/code><\/span>Code language:<\/span> Go<\/span> (<\/span>go<\/span>)<\/span><\/small><\/pre>\n\n\n
The type<\/code> can be of numeric types, strings, and booleans. For example:<\/p>\n\n\n
const<\/span> salesTax float64<\/span> = 0.08<\/span><\/code><\/span>Code language:<\/span> Go<\/span> (<\/span>go<\/span>)<\/span><\/small><\/pre>\n\n\n
Since Go can infer the type of the salesTax<\/code> using the initial value, you can make the code more concise as follows:<\/p>\n\n\n
const<\/span> salesTax = 0.08<\/span><\/code><\/span>Code language:<\/span> Go<\/span> (<\/span>go<\/span>)<\/span><\/small><\/pre>\n\n\n
As mentioned earlier, you cannot change the value of a constant. The following will result in a compile error:<\/p>\n\n\n
const<\/span> salesTax = 0.08<\/span>\nsalesTax = 0.09<\/span> \/\/ error<\/span><\/code><\/span>Code language:<\/span> Go<\/span> (<\/span>go<\/span>)<\/span><\/small><\/pre>\n\n\n
To declare multiple constants at the same time, you can use the const<\/code> block:<\/p>\n\n\n
const<\/span> (\n    salesTax = 0.08<\/span>\n    discount = 0.05<\/span>\n    greeting = \"Hi, there\"<\/span>\n)<\/code><\/span>Code language:<\/span> Go<\/span> (<\/span>go<\/span>)<\/span><\/small><\/pre>\n\n\n
The following example shows how to declare a constant based on the value of another constant:<\/p>\n\n\n
package main\n\nimport<\/span> \"fmt\"<\/span>\n\nfunc main() {\n    const<\/span> (\n        message = \"Hi\"<\/span>\n        size    = len(message) \/\/ 2<\/span>\n    )\n\n    fmt.Println(message, size)\n}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Hi 2<\/code><\/span><\/pre>\n\n\n
Summary<\/h2>\n\n\n\n
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  • Use Go constants to represent values that do not change throughout the program.<\/li>\n<\/ul>\n
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