Detailed introduction to how to use Golang to implement delayed execution

Golang is a new programming language. Many programmers like to use this language to develop applications because it has the advantages of efficiency, maintainability, and scalability. In Golang, delayed execution is a very useful feature that can help us improve code execution efficiency and reduce code complexity. This article will introduce in detail how to use Golang to implement delayed execution.

What is deferred execution?

In Golang, delayed execution refers to temporarily "delaying" the execution of certain statements during the running of the program, and then executing these statements until the program reaches a specific location. Delayed execution is implemented through the defer statement. When the program executes a defer statement, the statement will not be executed immediately, but will be placed on a stack. When the function returns, all defer statements will be taken out of the stack and executed in a last-in-first-out order.

The main functions of delayed execution are as follows:

1. Release of resources

We often need to open files, create connections, allocate memory, etc. during the programming process , these resources need to be released in time after use, otherwise it will easily lead to resource leakage. Using delayed execution can avoid forgetting to release resources and ensure that resources are released correctly.

2. Error handling

During the running of the program, various errors may occur. We need to handle them in time when errors occur to avoid program exceptions. Using delayed execution can automatically perform cleanup work when the program exits abnormally to prevent the program from leaving dirty data.

3. Performance Optimization

Some operations need to be executed under specific conditions, and this condition may occur during the running of the program. Using delayed execution can avoid judgment and improve the execution efficiency of the program.

How to use delayed execution

The defer statement in Golang is very simple. You only need to add defer before the statement that needs to be delayed. The following is a simple example:

func foo() {
    defer fmt.Println("world")
    fmt.Println("hello")
}

In the above code, we use defer in function foo to implement delayed execution. When the defer statement is executed, the program will not output "world" immediately. Instead, it will output "hello" first, and then output "world" when the function returns. The execution results are as follows:

hello
world

Delayed execution can be used to release resources. The following is an example of using defer to release resources:

file, err := os.Open("filename.txt")
if err != nil {
    log.error(err)
}
defer file.Close()

In the above code, we use The defer statement is used to release file resources. When the program is finished running, the file.Close() function will be automatically called to release the file resources.

Execution order of delayed execution

In Golang, if there are multiple defer statements, their execution order is last in, first out. That is to say, the last defer statement will be executed first, and so on, until the first defer statement is executed.

The following is an example of using multiple defer statements:

func foo() {
    defer fmt.Println("one")
    defer fmt.Println("two")
    defer fmt.Println("three")
    fmt.Println("hello")
}

The execution results are as follows:

hello
three
two
one

In the above code, we use three defer statements , they are executed in last-in-first-out order when the function returns.

Notes on delayed execution

When using the defer statement, you need to pay attention to the following issues:

1. When using the defer statement, you need to ensure that the function being called is executable. If the called function will cause the program to crash, the program will continue to execute, but the defer statement calling the function will not be executed.

2. The execution efficiency of the defer statement is not high. When efficient code execution is required, the defer statement should be avoided.

3. The defer statement will only be executed when the function returns. If the function using the defer statement does not return, then these defer statements will not be executed.

Summary

Delayed execution in Golang is a very useful feature that can help us achieve resource release, error handling, performance optimization, etc. When using the defer statement, you need to pay attention to issues such as the execution efficiency and executability of the called function and whether the function has a return value. If the defer statement is used correctly, it can improve the maintainability and readability of the program, effectively avoid program exceptions, and improve program execution efficiency. It is a skill that Golang programmers cannot miss.

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