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Adding Type Parameters to Struct Types

Explore how to enhance Go structs with type parameters to support generic programming. Understand creating generic adapters to sort slices of any struct type using Go's sort.Interface. Learn to handle type inference, implement comparison functions, and avoid common generics pitfalls for efficient and reusable code.

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Earlier, we wrote a generic function for sorting slices called SortSlice(), but that has some limitations in that it can only handle slices that are based on types that meet the constraints in constraints.Ordered. Oftentimes, we might want to handle slices that might contain types based on struct, say, for example, this type:

Go (1.18.2)
type Record struct {
    First, Last string
}

Our SortSlice() function could not handle a []Record, so we need to do something different to handle these types of cases.

For this example, we want to use Go's built-in sort.Sort() function. This is a highly optimized sort that uses multiple sorting algorithms, depending on slice size.

To use it, we need a type that implements the sort.Interface type. That interface type is defined as follows:

Go (1.18.2)
type Interface interface {
    Len() int
    Less(i, j int) bool
    Swap(i, j int)
}

Before Go generics, we would have needed to implement an adapter type to implement these for every type we wanted to sort. For example, here is an adapter to sort []int:

Go (1.18.2)
type intAdapter struct {
    sl []int
}
func (in intAdapter) Len() int {
    return len(in.sl)
}
func (in intAdapter) Swap(i, j int) {
    in.sl[i], in.sl[j] = in.sl[j], in.sl[i]
}
func (in intAdapter) Less(i, j int) bool {
    return in.sl[i] < in.sl[j]
}

And we could use it like this:

Go (1.18.2)
func main() {
	ints := []int{5, 3, 7, 1}
	sort.Sort(intAdapter{ints})
	fmt.Println(ints)
}

We would then need to do this for every other signed type or other types we wanted to sort. Imagine doing this for all int8, int16, int32, and int64 signed integer types.

We would also need to do that for every other type we want to sort. So, what we ...