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What are the functions in Golang? aiming at this problem, this article introduces the corresponding analysis and solution in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible way.

Function

The core design in the Go language, declared by the keyword func

The copy code is as follows:

Func funcName (input type1, input2 type2) (output1 type1, output2 type2) {

/ / logical code

Return value1, value2

}

Basic grammar

1. Grammar

The copy code is as follows:

/ / General function

Func func_name (an int) {

Println (a)

}

/ / multiple parameters, no return value

Func func_name (a, b int, c string) {

Println (a, b, c)

}

/ / single return value

Func func_name (a, b int) int {/ / the same type, a, b int can be omitted

Return a + b

}

/ / multiple return values

Func func_name (a, b int) (c int, err error) {/ / the return value can also be (int, error)

Return aquib, nil

}

Func SumAndProduct (A, B int) (int, int) {

Return B, A B

}

two。 Description:

The copy code is as follows:

Keyword func declaration

There can be one or more parameters, each followed by a type, and multiple values can be returned by the "," delimited function

Returns a value declaration, which can declare only the type

If there is no return value, you can omit the last return information

If there is a return value, you must add return to the outer layer

The Go function does not support nesting (nested), overloading (overload) and default parameters (default parameters)

Support:

1. No need to declare prototype

two。 Variable length parameter

3. Multiple return value

4. Name the return value parameter

5. Anonymous function

6. Closure

Note:

The function starts with func, and the left curly braces cannot start on another line.

Functions that begin with lowercase letters are visible in this package, so functions that begin with uppercase letters can be called by other packages.

Multiple return values and named return parameters

Multiple results can be returned like python, but not tuple

For unwanted return values, you can throw the trash can _

If you return parameters with a name, the return statement can be empty. Return is not empty, and the order of return values is the order of return rather than the order declared in the function header.

The copy code is as follows:

Package main

Func change (a, b int) (x, y int) {

X = a + 100

Y = b + 100

Return / / 101, 102

/ / return x, y / / ditto

/ / return y, x / / 102, 101

}

Func main () {

A: = 1

B: = 2

C, d: = change (a, b)

Println (c, d)

If the named return parameter is overridden by a variable with the same name in the code block, the result must be returned using explicit return

There is no need to force naming the return value, but the named return value can make the code clearer and more readable

Parameter passing: passing values and pointers

Pointer, Go keep pointer, use "." Instead of "- >" operation pointer target object member operator

The copy code is as follows:

& take the variable address

* access the target function indirectly through pointers

Func add1 (an int) int {

A = a + 1

Return a

}

X: = 3

X1: = add1 (x)

X / / 3

X1 / / 4

Pass the value, the value of x1 has not changed

Func add2 (a * int) int {

* a = * a + 1

Return * a

}

X: = 3

X1: = add2 & x)

X / / 4

X1 / / 4

Passing pointers to multiple functions can operate on the same object

Passing pointers is more lightweight (8byte), just passing memory addresses. We can use pointers to pass large structures.

In the Go language, the implementation mechanism of the three types of string,slice,map is similar to the pointer, so it can be passed directly without passing the pointer after taking the address.

Note that if the function needs to change the slice length, it still needs to take the address and pass the pointer.

Parameter passing: variable parameter

A variable parameter is essentially a slice and must be the last parameter.

When passing slice to a variable parameter function, be careful to use … Expand, otherwise it will be treated as a single parameter of dang, similar to python

The copy code is as follows:

Package main

Func sum (s string, args... int) {

Var x int

For _, n: = range args {

X + = n

}

Println (s, x)

}

Func main () {

Sum ("1, 2, 3 =", 1, 2, 3)

X: = [] int {0pm 1pm 2pm 3je 4}

Sum ("0-1-2-3 =", x [: 4]...)

}

The type type can only exist as a parameter type of a function and is the last parameter.

Is essentially an array slice, that is, [] type

Any type of indefinite parameter

The copy code is as follows:

Func Printf (format string, args... interface {}) {

}

Anonymous function

The copy code is as follows:

F: = func (xQuery y int) int {

Return x + y

}

Function as value, type

In the GE language, a function is also a variable, which can be defined by type. Its type is that all have the same parameters and the same return value.

Grammar

The copy code is as follows:

Type typeName func (input1 inputType1, input2 inputType2 [,....]) (result1 resultType1 [,....])

Usage e.g.1

The copy code is as follows:

Type testInt func (int) bool / / declares a function type

Func filter (slice [] int, f testInt) [] int {

Var result [] int

For _, value: = range slice {

If f (value) {

Result = append (result, value)

}

}

}

Func isOdd (integer int) bool {

If integer% 2 = = 0 {

Return false

}

Return true

}

Filter (a, isOdd)

This usage is very useful when writing interfaces.

Usage e.g.2

You can define a function type, or you can pass a function as a value (default value nil)

The copy code is as follows:

Package main

/ / define the function type callback

Type callback func (s string)

/ / define a function that can accept another function as an argument

/ / sum is the parameter name, and func (int, int) int is the parameter type

Func test (a, b int, sum func (int, int) int) {

Println (sum (aPerm b))

}

Func main () {

/ / Demo 1

Var cb callback

Cb = func (s string) {

Println (s)

}

Cb ("hello world")

/ / Demo 2

Test (1,2, func (a, b int) int {return a + b})

}

Results:

The copy code is as follows:

Hello world

three

This is the answer to the question about what the function in Golang is. I hope the above content can be of some help to you. If you still have a lot of doubts to be solved, you can follow the industry information channel to learn more about it.

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