How to define and use global variables in Golang

Golang is an efficient programming language that supports the use of global variables and functions. Global variables are variables that are visible to the entire program and are usually used to store data that needs to be shared within the program. How to define and use global variables in Golang?

First of all, the syntax for defining global variables in Golang is as follows:

var variable_name variable_type [ = value ]

Among them, variable_name is the name of the global variable, variable_type is the type of the variable , value is an optional variable initial value. For example, we define a global variable of string type:

var globalString string = "Hello, world!"

When defining global variables, you need to pay attention to the following points:

1. Global variables must use the keyword var to declare;
2. Global variables can be accessed by all functions, so special attention needs to be paid to the scope and naming convention of global variables;
3. If no initial value is given, the global variable will be Initialized to zero value (integer is 0, Boolean value is false, string is empty string, etc.);
4. Golang supports type deduction and can automatically deduce the variable type based on the initial value, for example:

var globalInt = 42
var globalFloat = 3.1415926

In the above code, the types of variables globalInt and globalFloat are int and float64 respectively.

In addition to defining global variables, you can also define global functions outside the function. Global functions are functions that do not belong to any structure or type and can be called by the entire program. The syntax for defining a global function is as follows:

func function_name() {
    // 函数体
}

For example, we define a function that prints the value of a global variable:

func printGlobalString() {
    fmt.Println(globalString)
}

It should be noted that when calling a global variable in a global function, you do not need to use var Re-declare the keyword and use the variable name directly.

In addition to directly defining global variables and functions, Golang also provides a package-level way to define global variables and functions. In Golang, a package is a collection of related functions. The variables and functions inside the package can be accessed by other files in the package. Within the same package, we can define global variables and functions in the following way:

package main

var (
    globalString string = "Hello, world!"
)

func printGlobalString() {
    fmt.Println(globalString)
}

In the above code, we define a variable globalString and function printGlobalString at the package level (), which can be accessed in other files within the package.

In short, it is very convenient to define global variables and functions in Golang. You only need to use the keywords var or func to complete the definition. However, since global variables and functions can be accessed by the entire program, special attention needs to be paid to their scope and naming conventions to avoid problems such as naming conflicts.

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