Go - Arrays, Slices, Maps

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Try it: Create a slice of three strings and append a fourth. Print length and contents.

Arrays

var a [3]int
b := [3]int{1,2,3}

Slices

s := []int{1,2,3}
s = append(s, 4)
sub := s[1:3] // shares backing array

Maps

m := map[string]int{"a":1}
m["b"] = 2
v, ok := m["c"] // ok=false if missing

Gotchas

Slices share backing arrays; copying vs referencing matters.
Maps are reference types; reading missing keys yields zero value with ok=false.

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Common errors

Confusing arrays with slices: arrays have fixed length; slices are dynamic views over arrays.
Modifying a subslice affects the original due to shared backing array.

Practice

Given s := []int{1,2,3}, create t := s[1:] and change t[0]. Inspect s and t.

Quick quiz

How do you check if a key exists in a map?

Show answer

v, ok := m[key] — ok is false if missing.