Why Can\'t You Get the Address of a Map Value in Go?

Why is the Address of a Map Value Unavailable in Go?

It is commonly surmised that maps in Go are backed by an immutable structure, preventing the retrieval of a reference to a map value. However, this is not the underlying reason.

The Role of Buckets

Maps in Go utilize bucket memory structures. A hash function directs each key to a primary bucket. Subsequently, keys and values are stored within either the primary bucket or an overflow bucket. The map buckets undergo continuous reorganization as elements are added, altered, or removed from the map.

Central Issue

The crux of the inability to access the address of a map value lies in the transient nature of map entries. Unlike fixed memory locations, map entries are nomadic, dynamically adapting to map operations. This characteristic precludes the possibility of referencing a definite memory location for a map value.

Contrasting with Slices

Contrary to the assertion that maps and slices are comparable in terms of memory structures, slices operate differently. Slices are backed by a dedicated array that stores its elements. Consequently, slices can be accessed directly through this underlying array, allowing modifications in place.

Consequences

The inability to access the address of a map value necessitates indirect modifications. To alter a map value, one must extract the value, manipulate it, and then reinstate it into the map. This extra step is an inherent limitation of maps resulting from their dynamic nature.

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