list.go 源码
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
// For more tutorials : https://learngoprogramming.com
// In-person training : https://www.linkedin.com/in/inancgumus/
// Follow me on twitter: https://twitter.com/inancgumus
package main
import (
"sort"
"strings"
)
// product is now *product because sorting will unnecessarily copy the product values
type list []*product
func (l list) String() string {
if len(l) == 0 {
return "Sorry. We're waiting for delivery 🚚.\n"
}
var str strings.Builder
for _, p := range l {
// fmt.Printf("* %s\n", p)
str.WriteString("* ")
str.WriteString(p.String())
str.WriteRune('\n')
}
return str.String()
}
func (l list) discount(ratio float64) {
for _, p := range l {
p.discount(ratio)
}
}
// implementation of the sort.Interface:
// by default `list` sorts by `title`.
func (l list) Len() int { return len(l) }
func (l list) Less(i, j int) bool { return l[i].title < l[j].title }
func (l list) Swap(i, j int) { l[i], l[j] = l[j], l[i] }
// byRelease sorts by product release dates.
type byRelease struct {
// byRelease embeds `list` and reuses list's Len and Swap methods.
list
}
// Less takes priority over the Less method of the `list`.
// `sort.Sort` will first call this method instead of the `list`'s Less method.
func (br byRelease) Less(i, j int) bool {
// `Before()` accepts a `time.Time` but `released` is not `time.Time`.
return br.list[i].released.Before(br.list[j].released.Time)
}
/*
Anonymous embedding means auto-forwarding method calls to the embedded value:
func (br byRelease) Len() int { return br.list.Len() }
func (br byRelease) Swap(i, j int) { br.list.Swap(i, j) }
*/
func byReleaseDate(l list) sort.Interface {
return &byRelease{l}
}
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