Cannot Range Over Expression

Why This Happens

The range clause in Go works with a limited set of types: slices, arrays, maps, strings, and channels. If you try to range over a struct, integer, or other unsupported type, the compiler will reject it. You may need to convert your data to a slice first.

The Problem

type MyList struct {
    items []int
}

func main() {
    list := MyList{items: []int{1, 2, 3}}
    for _, v := range list { // cannot range over list
        fmt.Println(v)
    }
}

The Fix

func main() {
    list := MyList{items: []int{1, 2, 3}}
    for _, v := range list.items {
        fmt.Println(v)
    }
}

Step-by-Step Fix

1. 1

   Identify the type

   Check the type of the variable you are trying to range over.

2. 2

   Find the iterable field

   If the variable is a struct, find the slice, map, or array field you actually want to iterate.

3. 3

   Range over the correct value

   Change the range expression to target the iterable field or convert the data to a rangeable type.