Go Pointers: When to Use `&` (Address Of) vs. `*` (Dereference) in Functions?

Understanding the Use of & and * Pointers in Go Functions

In Go development, it's sometimes necessary to pass variables as arguments to functions. However, certain scenarios may trigger compiler errors. This can be resolved by utilizing either & (address of) or * (dereference) pointers. Understanding the distinction between them is crucial.

Difference between & and * Pointers

The & operator returns the address of a variable, while the * operator dereferences a pointer, pointing to the data at the referenced address.

Usage

• & (Address of): Used when you want to pass the memory location of a variable (its pointer) as an argument. This is common when the function expects to operate directly on the data and potentially modify it.
• * (Dereference): Used when you want to access the data stored at the address pointed to by a pointer variable. This allows you to manipulate the actual data, rather than its memory location.

Example

Let's consider the following code:

func SendNotification(rw http.ResponseWriter, req *http.Request, p httprouter.Params) {

    decoder := json.NewDecoder(req.Body)

    var u User

    if err := decoder.Decode(&u); err != nil {
        http.Error(rw, "could not decode request", http.StatusBadRequest)
        return
    }
}

In this example, we're using the Decode function from the json package. This function expects a pointer to a User struct as an argument. Without the & operator, the compiler would throw an error.

Conclusion

Understanding the difference between & and * pointers is essential for effective Go programming. By correctly applying them, developers can resolve compiler errors and efficiently work with variables as arguments in functions, enabling data manipulation and communication in Go applications.

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