| Sometimes we'll want to sort a collection by something other than its natural order. For example, suppose we wanted to sort strings by their length instead of alphabetically. Here's an example of custom sorts in Go. | ||
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 corresponding type. Here we've created a `byLength` type that is just an alias for the builtin `[]string` type. | type byLength []string |
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| We implement `sort.Interface` - `Len`, `Less`, and `Swap` - on our type so we can use the `sort` package's generic `Sort` function. `Len` and `Swap` will usually be similar across types and `Less` will hold the actual custom sorting logic. In our case we want to sort in order of increasing string length, so we use `len(s[i])` and `len(s[j])` here. | 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 custom sort by converting the original `fruits` slice to `byLength`, and then use `sort.Sort` on that typed slice. | 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) |
[kiwi peach banana] |
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} |