Why Can't I Use Pointer Receivers on Map Entries in Go?

Dereferencing a Map Index in Go

Within a Go program, map indices cannot be referenced directly. This issue arises due to the dynamic nature of maps, where the address of an entry may change during map growth or shrinkage. As a result, attempting to call pointer receiver methods on map entries leads to the following error:

cannot call pointer method on f[0]
cannot take the address of f[0]

To resolve this issue, simply remove the asterisk (*) from the method receiver in the problematic method:

func (c Cashier) Buy(itemNum int){
    item, pass := c.items[itemNum]

    if pass{
        if item.amount == 1{
            delete(c.items, itemNum)
        } else{
            item.amount--
            c.items[itemNum] = item 
        }
        c.cash++
    }
}

By doing so, the method is no longer a pointer receiver, allowing it to be called on map entries without issue.

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