单值上下文中的多值strconv.ParseInt（）

Question

I have the following code:

var i2 uint64;
var err error;
i2, err = uint64(strconv.ParseInt(scanner.Text(), 64, 64));

And I received the error:

multiple-value strconv.ParseInt() in single-value context

According to everything I found on the Internet, this means that I am ignoring the two parameters returned by ParseInt, but I am using err. I know that maybe the mistake is very stupid, but I just started to learn Go and this confused me a lot.

Answer 1

The expression uint64(...) is a type conversion , and it cannot have multiple arguments (operands), but since strconv.ParseInt() has 2 return values, you're basically passing both to the type conversion, which is not valid.

Instead do this:

i, err := strconv.ParseInt(scanner.Text(), 64, 64)
// Check err
i2 := uint64(i)

Note that the base cannot be greater than 36 , so you'll definitely get an error as you're passing 64 as the base.

Or use strconv.ParseUint() which will return you an uint value right away:

i, err := strconv.ParseUint(scanner.Text(), 16, 64)
// i is of type uint64, and ready to be used if err is nil

(Here I used a valid, 16 base. Use whatever you have to.)

Also see related question+answer: Go: multiple value in single-value context

Answer 2

multiple-value strconv.ParseInt() in single-value context

ParseInt returns 2 values: integer and error. So you cannot use them in function argument where only one value allowed. You may first get value and error then use value in next operations.