How to Initialize String Pointers in Go Structs?

Initializing String Pointers in Structs

Initializing a string pointer in a struct can be challenging, especially when you need the pointer to be nil when unset. The following code snippet demonstrates an attempt to initialize a struct with a default string pointer value:

type Config struct {
  Uri       *string
}

func init() {
  var config = Config{ Uri: "my:default" }
}

However, this code fails with the error:

cannot use "string" (type string) as type *string in field value

This error occurs because you cannot get the address (to point) of a constant value. To resolve this issue, you can define a variable and pass its address instead. Here's how:

type Config struct {
  Uri       *string
}

func init() {
  v := "my:default"
  var config = Config{ Uri: &v }
}

Now, the initialization succeeds because v is a variable whose address can be obtained using the & operator. This allows you to point the Uri field to a nil value when unset or to a specific string value when set.

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