CODEWITHSUNDEEP
go
BigDataLearner
BigDataLearner

Reputation: 1468

How to sort by time.Time

I am trying to sort struct in Go by its member which is of type time.Time. the structure is as follows.

type reviews_data struct {
    review_id string
    date time.Time
    score int
    firstname string
    anonymous bool
    review_text string
    title_text string
    rating float64
    upcount int
}

I have the below functions for sorting 

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] 
}

A map is defined as follows

var reviews_data_map = make(map[string]reviews_data)

After the map gets filled with values,sorting of the map by values is done as below

//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)

The problem is that the result is not sorted.Can anyone tell me what the problem is.

Upvotes: 44

Views: 59152

Answers (5)

user2602152
user2602152

Reputation: 797

Go 1.21 update

You can now use slices.SortFunc for any type and the builtin Time.Compare function:

slices.SortFunc(yourSlice, func(a, b T) int { return a.Date.Compare(b.Date) })

Ref:

Upvotes: 11

Myrachanto
Myrachanto

Reputation: 11

sorting dates

type Location struct {
  Lat     float64   `json:"lat"`
  Lng     float64   `json:"lng"`
  Thetime time.Time `json:"thetime"`
}
func sorttime(dat []Location) {
  for i := 0; i < len(dat); i++ {
    for j := i + 1; j < len(dat); j++ {
      if dat[i].Thetime.Unix() < dat[j].Thetime.Unix() {
        dat[i], dat[j] = dat[j], dat[i]
      }
    }
  }
}

Upvotes: 0

camccar
camccar

Reputation: 730

This can be done below go 1.8 without the extra type and map in the accepted answer.

package main

import (
    "fmt"
    "time"
    "sort"
)

type reviews_data struct {
    review_id   string
    date        time.Time
}

func main() {
    fmt.Println("Sort Example")
    var listOfReviews = make([]reviews_data, 0)
    listOfReviews = append(listOfReviews, reviews_data{review_id: "1",date:time.Now()})
    listOfReviews = append(listOfReviews, reviews_data{review_id: "2",date: time.Now().AddDate(0, 0, 7*1)})
    listOfReviews = append(listOfReviews, reviews_data{review_id: "1",date: time.Now().AddDate(0, 0, 7*-1)})

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

Upvotes: 5

SevenJ
SevenJ

Reputation: 1561

Go 1.8 and above:

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

Upvotes: 110

peterSO
peterSO

Reputation: 166724

It looks sorted to me:

package main

import (
    "fmt"
    "sort"
    "time"
)

type reviews_data struct {
    review_id   string
    date        time.Time
    score       int
    firstname   string
    anonymous   bool
    review_text string
    title_text  string
    rating      float64
    upcount     int
}

type timeSlice []reviews_data

func (p timeSlice) Len() int {
    return len(p)
}

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

func (p timeSlice) Swap(i, j int) {
    p[i], p[j] = p[j], p[i]
}

func main() {
    var reviews_data_map = make(map[string]reviews_data)
    reviews_data_map["1"] = reviews_data{date: time.Now().Add(12 * time.Hour)}
    reviews_data_map["2"] = reviews_data{date: time.Now()}
    reviews_data_map["3"] = reviews_data{date: time.Now().Add(24 * time.Hour)}
    //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)
    }
    fmt.Println(date_sorted_reviews)
    sort.Sort(date_sorted_reviews)
    fmt.Println(date_sorted_reviews)
}

Output:

[{ {63393534000 0 0x1ba3e0} 0  false   0 0} { {63393490800 0 0x1ba3e0} 0  false   0 0} { {63393577200 0 0x1ba3e0} 0  false   0 0}]
[{ {63393490800 0 0x1ba3e0} 0  false   0 0} { {63393534000 0 0x1ba3e0} 0  false   0 0} { {63393577200 0 0x1ba3e0} 0  false   0 0}]

Upvotes: 28

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