《The Go Programming Language》 笔记

//sorting.go
package sorting

import (
    "fmt"
    "os"
    "sort"
    "text/tabwriter"
    "time"
)

type Track struct {
    Title  string
    Artist string
    Album  string
    Year   int
    Length time.Duration
}

type customSort struct {
    t    []*Track
    less func(x,y *Track) bool //自定义排序比较条件
}

func (cs *customSort) Len() int { return len(cs.t) }

func (cs *customSort) Less(i,j int) bool { return cs.less(cs.t[i],cs.t[j]) }

func (cs *customSort) Swap(i,j int) { cs.t[i],cs.t[j] = cs.t[j],cs.t[i] }

func SortTrack(tracks []*Track) {
    sort.Sort(&customSort{tracks,func(x,y *Track) bool {
        if x.Title != y.Title {
            return x.Title < y.Title
        }
        if x.Year != y.Year {
            return x.Year < y.Year
        }
        if x.Length != y.Length {
            return x.Length < y.Length
        }
        return false
    }})
    printTracks(tracks)
}


type byArtist []*Track

func (x byArtist) Len() int { return len(x) }

func (x byArtist) Less(i,j int) bool { return x[i].Artist < x[j].Artist }

func (x byArtist) Swap(i,j int) { x[i],x[j] = x[j],x[i] }

func SortTracksByArtist(tracks []*Track) {
    sort.Sort(byArtist(tracks))
    printTracks(tracks)
}

func printTracks(tracks []*Track) {
    const format = "%v\t%v\t%v\t%v\t%v\t\n"
    tw := new(tabwriter.Writer).Init(os.Stdout, 0, 8, 2,' ', 0)
    fmt.Fprintf(tw,format,"Title","Artist","Album","Year","Length")
    fmt.Fprintf(tw,"-----","-----")
    for _,t := range tracks {
        fmt.Fprintf(tw,t.Title,t.Artist,t.Album,t.Year,t.Length)
    }
    tw.Flush()
}

//main.go
var tracks = []*sorting.Track{
    {"Go","Deliah","From the Roots Up", 2012,length("3m38s")},{"Go","Moby", 1992,length("3m37s")},{"Go Ahead","Alicia Keys","As I Am", 2007,length("4m36s")},{"Ready 2 Go","Martin Soleving","Smash", 2011,length("4m24s")},}

func length(ts string) time.Duration {
    d,err := time.ParseDuration(ts)
    if err != nil {
        panic(ts)
    }
    return d
}

func main() {
    //sorting.SortTracksByArtist(tracks)
    sorting.SortTrack(tracks)
}