Easy way to get string pointers-CodePudding

A library I am using has a very weird API that often takes string pointers. Currently I am doing this:

s := "foobar"
weirdFun(&s)

to pass strings. Is there a way to do this without the variable?

CodePudding user response：

Maybe you should inform the author of the library, that the strings in Go are already references (to a structure, which is internally represented as a slice of runes), so no expensive copy operation is made by passing string to a function, it's call by reference. Hope this helps!

CodePudding user response：

The address operation &x can be used with addressable values. According to the language specification:

The operand must be addressable, that is, either a variable, pointer indirection, or slice indexing operation; or a field selector of an addressable struct operand; or an array indexing operation of an addressable array. As an exception to the addressability requirement, x may also be a (possibly parenthesized) composite literal.

So, you can work around this using a composite literal:

package main

import (
    "fmt"
)

func main() {
    s := "text"
    fmt.Printf("value: %v, type: %T\n", &s, &s)
    fmt.Printf("value: %v, type: %T\n", &[]string{"literal"}[0], &[]string{"literal"}[0])
}

Even though it's possible I don't recommend using this. This is not an example of clear code.

CodePudding user response：

The Azure SDK uses string pointers to distinguish between no value and the empty string.

Use Azure's StringPtr function to create a pointer to a string literal.

import (
    ⋮
    "github.com/Azure/go-autorest/autorest/to"
)

⋮
res, err := someClient.Create(ctx, someService.ExampleParameters{
    Location: to.StringPtr(location),
})

CodePudding user response：

The library is really weird, but you can do this in one line with function wrap, for example

func PointerTo[T ~string](s T) *T {
    return &s
}

s := "string"

weirdFun(PointerTo(s))