Pointers | Notion

"Pointers are simple: they just point to things. The complexity lies in understanding what they point to."

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Related Topics:

Arrays & Slices — Memory layout, append traps, value vs reference behavior
Maps — Reference type, no pointer needed for mutations </aside>

Overview

Go's pointer semantics sit between C's raw memory access and Java's fully managed references. Understanding when Go passes by value vs. reference is essential for writing correct, efficient code.

Core Concepts

Topic	Key Insight
Slices & Headers	Slices are headers (ptr, len, cap) — not the data itself
Pointer Nuances	Method receivers, nil checks, range loops, escape analysis
Advanced Patterns	Optional values, JSON omitempty, atomics, config merging

Quick Reference

When You Need Pointers

Operation	Pointer?	Why
`s[i] = x`	❌ No	Modifying existing data
`s = append(s, x)`	✅ Yes	Changes len/cap
`s = s[:n]`	✅ Yes	Changes len
`m["key"] = x`	❌ No	Maps are reference types
Struct method that mutates	✅ Yes	Pointer receiver needed

Reference Types (No Pointer Needed for Element Access)

Slices — for modifying elements
Maps — for adding/modifying entries
Channels — for sending/receiving

Value Types (Copied When Passed)

Arrays — fixed size, entire array copied
Structs — all fields copied
Primitives — int, float, bool, string