How to Initialize a Struct with a String Pointer and Allow for Nil Values?

Struct Pointer Initialization

Initializing a struct with a string pointer can be tricky, especially when the default value should be nil.

Problem

When attempting to initialize a struct with a string pointer as a default value, using a constant string in the initialization, an error occurs:

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

Solution

To initialize a struct with a string pointer that can be nil, you must assign the address of a variable, not a constant value, to the pointer. Here's a modified code that works:

type Config struct {
  Uri       *string
}

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

In this case, the variable v holds the default string value. By taking its address using the & operator and assigning it to Uri, we're creating a string pointer that can be used for comparisons and can be nil if not explicitly set.

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