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Golang Convert Map to Slice

Convert a map to a slice of keys, a slice of values, a slice of pairs and a flattened slice.

Convert map, slice. A map is ideal for fast lookups—we can find, add and remove elements with great speed. But it is not good for iterating (looping) over elements.mapSlice

Slice forms. We sometimes want a slice of keys, values, or pairs. And a "flat slice" one where all the keys and values are stored together one after another is also helpful.

Example program. Consider this program. We begin with a map of string keys and string values—it contains some common vocabulary words.

Keys: We get the keys from the map by using "range" and appending to an empty slice with append().

Values: Next we get the values from the map with range. We ignore the key in each iteration as we do not need it.

Pairs: Suppose we want a slice of 2-element string arrays. We can create these in a slice of pairs.

Flat: Here we place all the keys and values one after another in a flattened slice. This is easy to loop over.

Golang program that converts map to slices package main import "fmt" func main() { // Create example map. m := map[string]string{ "java": "coffee", "go": "verb", "ruby": "gemstone", } // Convert map to slice of keys. keys := []string{} for key, _ := range m { keys = append(keys, key) } // Convert map to slice of values. values := []string{} for _, value := range m { values = append(values, value) } // Convert map to slice of key-value pairs. pairs := [][]string{} for key, value := range m { pairs = append(pairs, []string{key, value}) } // Convert map to flattened slice of keys and values. flat := []string{} for key, value := range m { flat = append(flat, key) flat = append(flat, value) } // Print the results. fmt.Println("MAP ", m) fmt.Println("KEYS SLICE ", keys) fmt.Println("VALUES SLICE", values) fmt.Println("PAIRS SLICE ", pairs) fmt.Println("FLAT SLICE ", flat) } Output MAP map[go:verb ruby:gemstone java:coffee] KEYS SLICE [java go ruby] VALUES SLICE [verb gemstone coffee] PAIRS SLICE [[ruby gemstone] [java coffee] [go verb]] FLAT SLICE [java coffee go verb ruby gemstone]

Some notes. We can extract data from a map by using for-range loops. When a map is iterated over in this kind of loop, we access each key and value.Forrange

A summary. Often constructs like slices that are "flattened" contain all keys and values together are useful in real programs. They may also be simpler to use.
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