How do pointer parameters in Golang functions work?

Pointer parameters allow functions to directly modify the value passed by the caller. This provides the following advantages: unnecessary duplication is avoided and efficiency is improved. Simplify the function interface without additional return values.

How pointer parameters in Go functions work

In Go, parameters passed to functions can be value types or Pointer type. Pointer parameters allow a function to modify the actual value passed by the caller.

Value type parameters

Value type parameters are just like regular parameters in other programming languages. When passed to a function, the function creates a copy of the variable. This means that the function cannot modify the actual value passed by the caller.

func increment(value int) {
    value++
}

This function accepts a value type parameter value. When the increment function returns, the value of the original variable remains unchanged.

Pointer type parameter

Pointer type parameter is a reference pointing to another variable. When passed to a function, the function gets direct access to the actual value. This means that the function can modify the actual value passed by the caller.

func incrementPointer(value *int) {
    *value++
}

This function accepts a pointer type parameter value. When the function is called, value will be resolved to a pointer to the actual value. Functions can modify the actual value by dereferencing the pointer (*).

Practical Case

Consider a use case where we need to sort the elements in a slice.

No pointer parameters

func sortSlice(slice []int) {
    sort.Ints(slice)
}

This function accepts a value type slice parameter slice. When sorting slice, the original slice is not modified. Therefore, the caller must manually assign the sorted slice to the original slice.

Use pointer parameters

func sortSlicePointer(slice *[]int) {
    sort.Ints(*slice)
}

This function accepts a pointer type slice parameter slice. When sorting *slice, the original slice is modified directly. Therefore, the caller does not have to manually assign the sorted slice to the original slice.

Advantages of pointer parameters

• Directly modify the value passed by the caller
• Avoid unnecessary copying and improve efficiency
• Simplified function interface, no additional return value required

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