Why Can't I Directly Call Methods with Pointer Receivers on Go Map Elements?

Accessing Map Elements with Pointer Methods

In Go, accessing map elements with methods that have pointer receivers can present challenges. This arises because map index expressions are not addressable. When one attempts to call a method on a map index expression, the compiler checks that the receiver type is a pointer. If it is not, a compile-time error is generated.

To understand the issue, consider the code snippet:

x := odsMap[segRef]
x.GetValue("@OriginDestinationKey")

This code successfully accesses the GetValue method on the variable x, which is assigned the map value for the key segRef.

However, the following code snippet will fail with a compile-time error:

odsMap[segRef].GetValue("@OriginDestinationKey")

The error message indicates that "cannot take the address of odsMap[segRef]". This is because Go maps are not designed to be addressable, allowing for optimizations and flexibility in map implementations.

To work around this limitation, there are several options:

• Store pointer values in the map: If the map values are pointers, the address of the map index expression can be used as the receiver for the method call.
• Assign to a temporary variable: Alternatively, the map value can be assigned to a temporary variable whose address can be taken. Subsequently, the method can be called on the temporary variable. Note that any modifications made to the pointed object by the method will not be reflected in the original map value.

While these solutions provide workarounds, it is generally recommended to use pointer values with methods that have pointer receivers in Go to avoid addr

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