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46 lines
1.3 KiB
Go
46 lines
1.3 KiB
Go
// Sometimes we'll want to sort a collection by something
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// other than its natural order. For example, suppose we
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// wanted to sort strings by their length instead of
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// alphabetically. Here's an example of custom sorts
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// in Go.
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package main
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import (
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"fmt"
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"sort"
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)
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// In order to sort by a custom function in Go, we need a
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// corresponding type. Here we've created a `byLength`
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// type that is just an alias for the builtin `[]string`
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// type.
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type byLength []string
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// We implement `sort.Interface` - `Len`, `Less`, and
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// `Swap` - on our type so we can use the `sort` package's
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// generic `Sort` function. `Len` and `Swap`
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// will usually be similar across types and `Less` will
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// hold the actual custom sorting logic. In our case we
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// want to sort in order of increasing string length, so
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// we use `len(s[i])` and `len(s[j])` here.
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func (s byLength) Len() int {
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return len(s)
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}
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func (s byLength) Swap(i, j int) {
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s[i], s[j] = s[j], s[i]
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}
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func (s byLength) Less(i, j int) bool {
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return len(s[i]) < len(s[j])
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}
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// With all of this in place, we can now implement our
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// custom sort by converting the original `fruits` slice
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// to `byLength`, and then use `sort.Sort` on that typed
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// slice.
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func main() {
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fruits := []string{"peach", "banana", "kiwi"}
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sort.Sort(byLength(fruits))
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fmt.Println(fruits)
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}
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