Arrays of Tables — Repeating Structured Items

The `[[name]]` double-bracket form

Arrays of tables solve a real config-file pain: 'a list of structured things, each with multiple fields, that I want to read or edit one at a time.' The syntax is double brackets: [[products]]. Every [[products]] block in the file appends one element to the products array.

When to reach for it

An array of items, each with multiple fields.
Items you want to comment, edit, or grep individually.
Where inline-table arrays would be too long to read.

The `[[]]` vs `[]` distinction

[server] opens the server table (singular). [[plugins]] appends one element to the plugins array. Each [[plugins]] is its own self-contained block; the order in source = the order in the array.

Principle: when in doubt, structure that reads as 'one of N things' should be an array of tables, not a table of tables keyed by name. Arrays preserve order; reviewers can comment on each item; new entries append cleanly. Compare to YAML — same idea, less reliable diffs.

Code

Array of tables — three plugins·toml

[[plugins]]
name = "auth"
version = "1.2"
enabled = true

[[plugins]]
name = "rate-limit"
version = "0.4"
enabled = true
config = { window_sec = 60, max = 100 }

[[plugins]]
name = "experimental"
version = "0.1"
enabled = false
# Disabled until the perf regression lands
# (see #142)

Equivalent inline-table form (uglier for many fields)·toml

plugins = [
  { name = "auth",         version = "1.2", enabled = true },
  { name = "rate-limit",   version = "0.4", enabled = true,  config = { window_sec = 60, max = 100 } },
  { name = "experimental", version = "0.1", enabled = false },
]
# Use inline form for 2-3 short fields; use [[plugins]] when items are bigger.

Nested arrays of tables (Hugo menus pattern)·toml

[[menu.main]]
name = "Home"
url = "/"
weight = 1

[[menu.main]]
name = "Posts"
url = "/posts"
weight = 2

[[menu.main]]
name = "About"
url = "/about"
weight = 3

Exercise

Convert a YAML list-of-objects (a list of CI jobs, a list of webhooks, a list of routes) into a TOML array of tables. Run the file through tomllib.load and confirm the parsed shape matches a list of dicts. Diff a 'add one new entry' commit in both forms — you should see TOML's noise-free diff win.

Arrays of Tables — Repeating Structured Items

The `[[name]]` double-bracket form

When to reach for it

The `[[]]` vs `[]` distinction

Code

External links

Exercise

Progress

Comments 0

The [[name]] double-bracket form

When to reach for it

The [[]] vs [] distinction

Code

External links

Exercise

Progress

The `[[name]]` double-bracket form

The `[[]]` vs `[]` distinction