Golang error: 'invalid use of ... operator' How to solve it?

For Golang developers, "invalid use of ... operator" is a common error. This error usually occurs when using variable-length parameter functions. It will be detected at compile time and indicate which parts have problems. This article will introduce how to solve this error.

1. What is a variable-length parameter function

The variable-length parameter function is also called a variable-length parameter function, which is a function type in the Golang language. Using a variable-length parameter function, you can define multiple parameters as follows:

func funcName(param ...type)

Among them, the "..." symbol indicates that the parameters are variable, Any number of parameters can be passed in. This feature is useful in certain situations, such as when a variable number of parameters needs to be processed.

2. Reason for “invalid use of … operator” error

When we pass parameters in a function, improper use will cause the compiler to report an “invalid use of … operator” error. Here are some common situations:

1. Using variable-length parameters in the parameter list:

You can use variable-length parameters when defining a function, but when passing them to function parameters The three-dot notation cannot be used. This is a common mistake:

func funcName(param ...type)
{
// some code
}

funcName(1, 2, 3 ...) // invalid use of ... operator

You can use the following code to pass parameters:

funcName(1,2,3)

2. Using variable-length parameters in slices

You cannot use three dots when creating slices. Here is an incorrect example:

arr := []int{1,2,3...}

should be replaced with:

arr := []int {1,2,3}

3. Using variable-length parameters in the array definition

You cannot use three dots in the array definition. Here is an example of the error:

arr := [3]int{1, 2, 3...}

You can replace it with the following code:

arr : = [3]int{1, 2, 3}

4. Using wrong parameter types when calling a function

If you use wrong parameters in a function call type, an "invalid use of ... operator" error will occur. For example:

func add(num int, nums ...int) int {

sum := num
for _, v := range nums {
    sum += v
}
return sum

}

add(1,"2",3)

This error can be solved by modifying the wrong parameter type, such as changing the string "2" to the integer 2.

3. Use variable-length parameters correctly

When you use variable-length parameter functions correctly, they can provide great convenience for your code. The following is a code example for the correct use of variable-length parameters:

func add(num int, nums ...int) int {

sum := num
for _, v := range nums {
    sum += v
}
return sum

}

sum := add( 1, 2, 3, 4, 5)

In this example, the add() function can accept any number of parameters and add them to return an integer. When calling the function we passed 6 parameters and stored the result in the variable sum.

Summary:

The "invalid use of ... operator" error is very common when encountering variable-length parameter functions. But with careful use, you can avoid these mistakes and use variadic parameters with ease. By learning the correct use of variadic parameters, you can take better advantage of Golang and implement efficient code.

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