GoLang - How to use maps

When we start in Go and we already developed in another language, we can be perturbed about how maps works.

Declaration

The object type map doesn't exist in Go. A key word exist instead and it helps to create an object type based on maps with the following structure:

map[]

Examples

map[string]string

For example, to create a map which will link a string key to a number, you will use : map[string]int

For a map used to link a rune to a book object : map[rune]book

Details on object type

As map object type doesn't directly exist, object types are identicals only if they have the same key type and value type.

map[rune]book != map[string]int
map[rune]book != map[string]book
map[rune]book != map[rune]int
map[rune]book == map[rune]book

Utilization

m := map[string]string{}   // Declare a map

m["p"] = 3                 // Add a value
m["p"] = 4                 // Update a value
fmt.Println(m)             // Print a map: "map[p:4]"

v := m["p"]                // Get a value: v == 4
v = m["p2"]                // Value not found: v == 0 (zero)

_, found := m["p"]         // found == true
_, found = m["p2"]         // found == false

if x, found := m["p"]; found {
    fmt.Println(x)
}                           // Print "4"

delete(m, "p")              // Delete a map

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I hope it will help you! 🍺

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