2.10.1. Function definition #

The format of Go language function definition is as follows:

func function_name( [parameter list] ) [return_types] {
   Function body
}

Function definition parsing:

• func : The function is composed of func begin to declare

• function_name : The function name, parameter list, and return value typeconstitute the function signature.

• parameter list : Parameter list, a parameter is like a placeholder. Whena function is called, you can pass a value to the parameter, which is calledthe actual parameter. The parameter list specifies the parameter type, order, and number of parameters. Parameters are optional, that is, functions can also contain no parameters.

• return_types : Returns the type, and the function returns a list of values return_types is the data type of the column value. Some functions do not need to return a value, in this case return_types is not necessary.

• Function body: a collection of code defined by a function.

2.10.2. Example #

The following example is max() function, which passes in two integer arguments num1 and num2 , returns the maximum values of these two parameters:

/* Function returns the maximum value of two numbers */
func max(num1, num2 int) int {
   /* Declare local variables */
   var result int
   if (num1 > num2) {
      result = num1
   } else {
      result = num2
   }
   return result
}

2.10.3. Function call #

When you create a function, you define what the function needs to do and call the function to perform the specified task.

Call the function, pass parameters to the function, and return a value, such as:

package main
import "fmt"
func main() {
   /* Define local variables */
   var a int = 100
   var b int = 200
   var ret int
   /* Call the function and return the maximum value */
   ret = max(a, b)
   fmt.Printf( "The maximum value is : %d\\n", ret )
}
/* Function returns the maximum value of two numbers */
func max(num1, num2 int) int {
   /* Define local variables */
   var result int
   if (num1 > num2) {
      result = num1
   } else {
      result = num2
   }
   return result
}

The maximum value is : 200

2.10.4. Function returns multiple values #

Go function can return multiple values, such as:

2.10.5. Example #

package main
import "fmt"
func swap(x, y string) (string, string) {
   return y, x
}
func main() {
   a, b := swap("Google", "Runoob")
   fmt.Println(a, b)
}

The execution result of the above example is:

Runoob Google

2.10.6. Function parameter #

If a function takes an argument, the variable can be called a formal parameter of the function.

A parameter is like a local variable defined in the body of a function.

To call a function, you can pass parameters in two ways:

By default Go language uses value passing, that is, the actual parameters are not affected during the call.

2.10.7. Function usage #