Go language functions as parameters of functions

Go Language functions are used as arguments to functions

• go Expressions for language functions
  func Function name （ The name of the parameter 1 type 1, The name of the parameter 2 type 2,…）（ Return type 1, Return type 2,…） {
  The body of the function
  }
  Be careful ：go Language functions support multiple return values . Capitalized function name means that the function is Public Can be used by other package call , Lowercase private, Cannot be called by other packages .

func myFunc(number1 int32,number2 int32) (int32,int32) {
    
  return number1+number2 ,number1 -number2 
}

• go Functions in a language have their own types .

package main
import (
	"fmt"
)
func addNumber(a1 int,a2 int) int {
    
	return a1+a2
}
func main()  {
    
	 fmt.Printf("addNumber The type is %T:",addNumber)
}

The execution result of the above code is ：

• go Languages can treat functions as data types , For example, declare a addNumber Variables of type are as follows ：

// Method 1
a1:=addNumber
// Method 2
// Statement a1 The type of func(int,int) int, And give the initial value addNumber
// Here is an analogy var a2 int=32,addNumber amount to 32 Is a constant , Given func(int,int) int Type specific values .
var a1 func(int,int) int=addNumber

• Function types are used as formal parameters of functions
  Such as , You can define one of the following functions ：

package main
import (
	"fmt"
)
func addNumber(a1 int,a2 int) int {
    
	return a1+a2
}
func addNumber2(a3 func(int,int) int,a4 int) int {
    
	return a3(a4,a4)+a4
}
func main()  {
    
	 //fmt.Printf("addNumber The type is %T:",addNumber)
	 fmt.Printf("addNumber2 The type is :%T\n",addNumber2)
	 fmt.Printf("addNumber2 The result of the implementation of :%v\n",addNumber2(addNumber,34))
}

The execution result is ：

Here we can simplify by using alias ：

package main
import (
	"fmt"
)

func addNumber(a1 int,a2 int) int {
    
	return a1+a2
}

type myFunc func(int,int) int

func addNumber2(a3 myFunc,a4 int) int {
    
	return a3(a4,a4)+a4
}

func main()  {
    
	 //fmt.Printf("addNumber The type is %T:",addNumber)
	 fmt.Printf("addNumber2 The type is :%T\n",addNumber2)
	 fmt.Printf("addNumber2 The result of the implementation of :%v\n",addNumber2(addNumber,34))
}

Notice that the function type has changed at this time , The execution result is ：