Why Can\'t I Assign to a Pair in a Go Map?

Understanding the "Can not assign to pair in a map" Error

When attempting to modify a field of a pair value within a map in Go, you may encounter an error message stating "can not assign to pair in a map." This error arises primarily due to the non-addressability of map values.

In Go, addressability refers to the ability to obtain the memory address of a variable or value. Addressability is essential for operations that involve modifying elements in a structured way, such as assigning a value to a field within a struct. However, map values are not addressable. This means that it is not possible to use the selector (.) operator to assign values to fields in a pair value within a map directly.

To overcome this limitation, you have two primary options:

• Use a pointer type as the map value (map[string]*pair): By using a pointer type, the indirection through the pointer satisfies the addressability requirement, allowing you to access and modify fields within the pair value.
• Copy or replace the existing pair value: Alternatively, you can create a copy of the existing pair value, modify the desired field in the copy, and then assign it back to the map. You can also replace the entire pair value with a new one containing the desired changes.

By understanding the non-addressability of map values and utilizing the alternative methods provided, you can effectively manipulate pair values within maps and avoid the "can not assign to pair in a map" error.

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