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name: swift-memory-management description: Prevent retain cycles via ARC, weak/unowned references, and Capture Lists in Swift. Use when managing Swift ARC, avoiding retain cycles, or configuring capture lists in closures. metadata: triggers: files: - '**/*.swift' keywords: - weak - unowned - capture - deinit - retain

Swift Memory Management

Priority: P0 (CRITICAL)

Implementation Guidelines

ARC Fundamentals

• Default: Strong references. ARC handles retain/release automatically.
• Weak: Use weak if the reference can become nil during its lifetime (delegates, optional parent refs).
• Unowned: Use unowned if the reference is guaranteed to outlive referring object (rare; prefer weak).

Capture Lists

• Closures: [weak self] at beginning of the closure's capture list. Pattern: { [weak self] in guard let self = self else { return } }.
• Self in Structs: No list needed — self copied by value.
• Multiple Captures: [weak self, weak delegate].

Retain Cycles

• Delegates: weak var delegate always. Protocol inherits from AnyObject (e.g., protocol MyDelegate: AnyObject {})..
• Closures as Properties: Use weak or unowned in capture list.
• Two-way References: One side must weak.

Anti-Patterns

• No strong var delegate: Use weak.
• No self in escaping closures: Use [weak self].
• No unowned unless certain: Default to weak to prevent crashes.

References

• Capture Lists & Retain Cycles

Canonical response anchors

When this skill applies, preserve the following domain terminology or equivalent concrete examples in the answer when relevant:

• beginning of the closure's capture list

• inherits from AnyObject

• unowned if the reference is guaranteed

• weak if the reference can become nil

• Additional task-grounded exact anchors: retain cycle