golang function returns error

Golang is an efficient, fast and reliable programming language. Programs written in Golang usually have excellent performance and reliability. However, when writing Golang code, encountering errors and exceptions is inevitable. Therefore, how to handle function return errors in Golang is a very important issue.

In Golang, when a function returns an error, it usually returns a value of type error. This value is usually defined as an interface type, which has only one method Error(), which returns a string type error description. When an error occurs during function execution, we can determine whether an error occurred by determining whether the returned error value is nil.

In Golang, functions can also return multiple values. Therefore, when returning an error from a function, you can pass the error return value as the last parameter of the function's return value. For example, we can define a function like this:

func Divide(dividend float64, divisor float64) (float64, error) {
    if divisor == 0 {
        return 0, fmt.Errorf("division by zero")
    }
    return dividend / divisor, nil
}

In this function, we first determine whether the divider is 0. If it is 0, return an error value. Otherwise, return the quotient of dividend and divider and a nil value. No errors.

When calling this function, we need to determine whether the returned error value is nil. If it is not nil, it means an error occurred when the function was executed, and we need to handle the error. For example, you can use the Println function in the fmt package to output errors to the console:

result, err := Divide(10.0, 0.0)
if err != nil {
    fmt.Println("Error:", err)
}

In this example, we call the Divide function and pass in the parameters 10.0 and 0.0. Since divisor is 0, the function will return an error value. We use the := operator to receive the return value of the function, and use the if statement to determine whether err is nil. Since err is not nil, we use the Println function in the fmt package to output the error to the console.

In addition to using the fmt package to output error information, we can also use the log package to record errors. The log package provides a set of functions that can write error information to log files or console output. For example, we can use the Println function in the log package to write errors to the log file:

func Divide(dividend float64, divisor float64) (float64, error) {
    if divisor == 0 {
        log.Println("Error: division by zero")
        return 0, fmt.Errorf("division by zero")
    }
    return dividend / divisor, nil
}

In this example, we use the Println function in the log package to write error information to the log file. This can help us better understand the execution of the program and provide help in analyzing and fixing errors.

In addition, if we want to customize the error type, we can create a custom error type by implementing the error interface. For example, we can define a custom error type like this:

type MyError struct {
    err string
}

func (e MyError) Error() string {
    return e.err
}

In this example, we define a MyError type and implement the Error() method. This method returns a string type error description. In this way, we can return a custom error type in the function:

func Divide(dividend float64, divisor float64) (float64, error) {
    if divisor == 0 {
        return 0, MyError{"division by zero"}
    }
    return dividend / divisor, nil
}

In this example, we return different error types depending on whether the divisor is 0. This error type is defined as the MyError type and contains a string type error description.

In short, error handling is very important in Golang. Error handling can be made easier and more reliable using Golang's built-in features. When a function returns an error, we can use the error type to handle it, use the fmt package or log package to output error information, or customize the error type to achieve a more flexible and customized error handling solution.

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