What is the variable scope of Golang function

The variable scope of Golang function refers to the visibility and life cycle of variables inside the function. According to the position and scope of variables in the function, variables can be divided into three types: local variables, parameter variables and return value variables. Detailed introduction: 1. Local variables are variables defined inside a function and can only be used inside the function. Their scope is limited to inside the function, including all code blocks and nested code blocks of the function; 2. Parameter variables , are the input parameters received by the function and can be used inside the function. Their scope is limited to the inside of the function, etc.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

In the Go language, the scope of a function refers to the visibility and life cycle of variables inside the function. According to the position and scope of variables in the function, variables can be divided into three types: local variables, parameter variables and return value variables.

1. Local Variables: Local variables are variables defined inside a function and can only be used inside the function. Their scope is limited to within the function, including all code blocks and nested code blocks of the function. When the function execution is completed, the life cycle of the local variable ends and its memory space will be released.

The following is an example showing the scope of local variables:

func exampleFunction() {  
    localVariable := 10 // 局部变量  
    fmt.Println(localVariable) // 可以访问局部变量  
}

In the above example, localVariable is a local variable and can only be used inside the exampleFunction function.

2. Parameter Variables: Parameter variables are input parameters received by the function and can be used inside the function. Their scope is limited to within the function, but the values ​​of external variables can be modified through parameter passing. When the function execution is completed, the life cycle of the parameter variable ends and its memory space will be released.

The following is an example showing the scope of parameter variables:

func add(a, b int) int {  
    return a + b // 可以访问参数变量  
}  
  
func main() {  
    x := 10  
    y := 20  
    result := add(x, y) // 将x和y作为参数传递给add函数  
    fmt.Println(result) // 输出30  
}

In the above example, the scope of the parameter variables a and b of the add function is limited to within the function, but can be passed Parameters are passed to modify the values ​​of external variables x and y.

3. Return Value Variables: The return value variable is the return value of the function and is used to store the output result of the function. Their scope is limited to within the function, but output can be passed through assignment to external variables. When the function execution is completed, the life cycle of the return value variable ends, but whether its memory space is released depends on the type of the external variable. If the external variable is a value type (such as integer, floating point number, string, etc.), the memory space of the return value variable will be released; if the external variable is a reference type (such as slice, map, channel, etc.), the memory space of the return value variable will be released. The memory space is not released, but passed to the external variable by reference.

The following is an example showing the scope of the return value variable:

func square(n int) int {  
    return n * n // 返回值变量  
}  
  
func main() {  
    result := square(5) // 将结果赋值给外部变量result  
    fmt.Println(result) // 输出25  
}

In the above example, the return value variable of the square function is a local variable, and its scope is limited to within the function . But by assigning a value to the external variable result, we can pass the output of the function to the external code block for use.

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