Arrays, Slices, and Maps

Arrays, Slices, and Maps

Go has three main collection types: arrays for fixed-size data, slices for flexible sequences, and maps for key-value lookup.

Arrays

Arrays have a fixed length and store values of one type.

var a [3]int
var b = [3]string{"a", "b", "c"}

Slices

Slices are views over arrays with dynamic length and capacity.

s := []int{1, 2, 3}
s = append(s, 4, 5)
sub := s[1:4]

Use len(s) for the number of elements and cap(s) for the current capacity.

Maps

Maps store values by key and are useful for lookup tables.

m := make(map[string]int)
m["alice"] = 42
fmt.Println(m["alice"])

Check whether a key exists using the second boolean result.

if v, ok := m["bob"]; ok {
    fmt.Println("found", v)
}