Can Go Struct Pointer Methods Reassign Pointers to Different Instances?

Can Pointers in Struct Pointer Methods Be Reassigned to Other Instances?

Understanding Pointers in Go

Pointers in Go, like integers, are values interpreted as memory addresses. To modify a variable of type int, a pointer to that pointer (int) is passed, and the pointed object (*i) is then assigned a new value.

Modifying Pointers in Struct Pointer Methods

However, struct receiver methods cannot be pointers to pointers (*T) for the receiver type. Instead, there are two options:

• Option 1: Non-Method Function

Define a non-method function that takes a **T pointer and modifies the pointed object.

• Option 2: Return the Modified Pointer

Return the modified pointer from the method, and have the caller assign it to the variable containing the tree pointer.

Addressing Concerns

Returning the modified pointer from a method is a common practice in Go. For instance, the append() function both appends elements to a slice and returns the modified slice, which the caller must assign.

Example Code

Using Option 1, the solution for rotating a tree left to its root would be:

func rotateLeftToRoot(ptree **AvlTree) {
    tree := *ptree
    if tree == nil {
        return
    }
    prevLeft := tree.left
    if prevLeft != nil {
        tree.left = prevLeft.right
        prevLeft.right = tree
        tree = prevLeft
    }
    *ptree = tree
}

Conclusion

While it's not recommended to reassign pointers in struct pointer methods in Go, the two options outlined above provide alternatives for modifying tree structures. Returning the modified pointer and having the caller assign it is a common and effective approach in Go programming.

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