How to Sort a Slice of Structs by Multiple Fields in Go?

Sorting Slice Objects by Multiple Fields

Sorting by Multiple Criteria

Consider the following Parent and Child structs:

type Parent struct {
    id       string
    children []Child
}

type Child struct {
    id string
}

Suppose we have a slice of Parent structs with predefined values:

parents := []Parent{
    {
        "3",
        []Child{
            {"2"},
            {"3"},
            {"1"},
        },
    },
    {
        "1",
        []Child{
            {"8"},
            {"9"},
            {"7"},
        },
    },
    {
        "2",
        []Child{
            {"5"},
            {"6"},
            {"4"},
        },
    },
}

Sorting Requirements:

Our goal is to sort the parents slice based on two criteria:

1. Sort Parent structs in ascending order of their id field.
2. Within each Parent struct, sort the children slice in ascending order of the id field.

Solution:

To achieve this sorting, we utilize the sort.Slice function, which provides a flexible way to sort slices based on custom comparison functions. Here's the code:

<code class="go">// Sort parents by their ID
sort.Slice(parents, func(i, j int) bool { return parents[i].id < parents[j].id })

// Iterate over each parent and sort their children by ID
for _, parent := range parents {
    sort.Slice(parent.children, func(i, j int) bool { return parent.children[i].id < parent.children[j].id })
}</code>

This sorting algorithm efficiently handles both criteria, ensuring that the parents slice is ordered as desired.

Expected Result:

The sorted slice should resemble the following structure:

[{1 [{7} {8} {9}]} {2 [{4} {5} {6}]} {3 [{1} {2} {3}]}]

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