更改类型后获取地址

Question

I am new to Go and I'm trying to find a convenient way from a developers perspective to get an address of an object after changing type.

Consider these two new types:

type specialString string
type nestedStruct struct {
    name *specialString
}

The canonical way I have found for filling in the nestedStruct is this:

str := "James"
specStr := specialString(str)
nested := nestedStruct{
    name: &specStr,
}

Is there a way to omit the declaration of specStr, which is then only used in one place? I tried this, but it triggers an syntax error (what is the logical reason for that?):

//Syntax error
nested := nestedStruct{
    name: &specialString(str),
}

Any help would be appreciated.

Answer 1

You cannot take the address of an arbitrary operation, including a type conversion. For details, see How can I store reference to the result of an operation in Go?; and Find address of constant in go.

You can omit one of the local variables if you convert the string literal:

specStr := specialString("James")
nested := nestedStruct{
    name: &specStr,
}

If you already have a variable of string type and you want to omit the second variable (of specialString type), then take the address of the existing string variable, and convert it to *specialString:

str := "James"
nested = nestedStruct{
    name: (*specialString)(&str),
}

Try these examples on the Go Playground.

If you want to omit the local variable, see this answer for options: How do I do a literal *int64 in Go?