How to Correctly Sort Structs Containing `time.Time` Fields in Go?

Sorting Structs by Time.Time in Go

Sorting structs based on member fields of type time.Time can be a common task in Go programming. To understand the solution, let's delve into the problem:

Problem:

When attempting to sort a struct with a time.Time member called date, using custom sorting functions, the resulting list remains unsorted.

Custom Sorting Functions:

You provided the following custom sorting functions:

type timeSlice []reviews_data

// Forward request for length
func (p timeSlice) Len() int {
    return len(p) 
}

// Define compare
func (p timeSlice) Less(i, j int) bool {
    return p[i].date.Before(p[j].date)
}

// Define swap over an array
func (p timeSlice) Swap(i, j int) {
    p[i], p[j] = p[j], p[i] 
}

These functions define a custom type timeSlice that implements the sort.Interface interface, required for sorting in Go.

Map Sorting:

You aimed to sort a map of type map[string]reviews_data by the date field of its values. Here's your sorting code:

//Sort the map by date
    date_sorted_reviews := make(timeSlice, 0, len(reviews_data_map))
    for _, d := range reviews_data_map {
        date_sorted_reviews = append(date_sorted_reviews, d)
    }       
    sort.Sort(date_sorted_reviews)

Solution:

The problem arises from the incorrect call to sort.Sort. For Go versions 1.8 and above, the recommended way to sort a slice is using sort.Slice:

sort.Slice(date_sorted_reviews, func(i, j int) bool {
    return date_sorted_reviews[i].date.Before(date_sorted_reviews[j].date)
})

This syntax explicitly defines the slice to be sorted and the sorting function. Using this updated code will correctly sort your structs by their date field.

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