Cannot Call Pointer Method on Value

Why This Happens

When a method is defined with a pointer receiver (*T), it can only be called on a pointer or an addressable value. If you have a non-addressable value like a map element or function return value, you cannot call pointer methods on it directly.

The Problem

type MyWriter struct{}

func (w *MyWriter) Write(data []byte) {}

func getWriter() MyWriter {
    return MyWriter{}
}

func main() {
    getWriter().Write([]byte("hello")) // cannot take address of return value
}

The Fix

func main() {
    w := getWriter()
    w.Write([]byte("hello")) // w is addressable
}

Step-by-Step Fix

1. 1

   Identify the receiver type

   Check if the method is defined on a pointer receiver (*T) or value receiver (T).

2. 2

   Find the non-addressable value

   Determine why the value cannot have its address taken (map element, function return).

3. 3

   Store in a variable

   Assign the value to a variable first so it becomes addressable, then call the method.