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flow-resource-patterns

Flow resource types and when to use each: Variables, Collection Variables, Constants, Formulas, Text Templates, Choices, Stages, Picklist Choice Sets, Record Choice Sets. Covers scope, data types, and reuse patterns. Triggers: 'which Flow resource type', 'record choice set or picklist choice set', 'choice collection from records in a Flow' (the choice-set wiring itself is flow/flow-dynamic-choices). NOT for decision elements. NOT for custom metadata (use admin/custom-metadata-types).

• v1.1.1
• Salesforce Spring '25+
• Updated 2026-10-02
• Operational Excellence
• Reliability

• flow
• variables
• formulas
• constants
• choice-sets
• text-template

Open the skill folder on GitHub

Flow Resource Patterns

Activate when designing or debugging a flow's data layer — variables, formulas, constants, collections, text templates, choice sets. Picking the right resource type avoids brittle assignment chains and makes the flow debuggable.

Before Starting

• Determine reuse vs one-off. Formulas recompute every reference and are ideal for derived values; assignments cache a value and are faster when referenced many times.
• Understand scope. All resources are flow-scoped — not global. Subflows need input/output variables.
• Think about null. Uninitialized variables return null, not zero or empty string.

Core Concepts

Variable vs Constant vs Formula

Collection variables

A collection holds multiple values of the same type (primitive or SObject).

• Primitive collection — Text[], Number[] — for filters, merge targets.
• SObject collection — Contact[] — for bulk DML.
• Add elements with Assignment + "Add" operator, or populate from Get Records.

SObject variables

Hold one record's fields. Initialized to null. Getting a single record populates an SObject variable; referencing a field on a null SObject throws NullPointerException-style error.

Text templates

Rich-text or plain-text blocks with merge fields. Primary use: email body, screen display. Plain-text mode needed for Send Email action if the recipient expects non-HTML.

Choice resources

Common Patterns

Pattern: Derived value as Formula (not Assignment)

Formula: Discounted_Amount = {!Amount} - {!Amount} * {!Discount_Rate}

Formulas stay synced; an Assignment value goes stale when inputs change.

Pattern: Collection-of-ids for IN-filter

Assignment: Add {!$Record.Id} to collection accountIds
Get Records: Contact where AccountId IN accountIds

Pattern: Email body as Text Template

Text Template with merge fields → referenced from Send Email Action Body. Easier to test than inline string concatenation in Assignments.

Pattern: Config via Constants (not hardcoded values)

Constant: DEFAULT_REGION = "NAMER"
Used in: 4 Decision elements and 1 Create Records field map

Swapping the constant in one place updates all references.

Decision Guidance

Choosing Between Choice Resources

Three Flow resources present a list of options and they are not interchangeable. A Choice is one hand-typed label and value — right for a fixed yes/no or a short constant list. A Picklist Choice Set reads a picklist field's active values at run time, so the Flow follows the field without redeploying; it cannot filter. A Record Choice Set reads records with a filter and sort, maps one field to the label and one to the stored value, and can assign the chosen record's other fields to variables; it is the resource for a dynamic choice collection driven by data. A collection variable of records is not a choice resource — to offer records as choices, bind a Record Choice Set to it. Dependent choices (one set filtered by another's selection) and the metadata shapes for all three are flow/flow-dynamic-choices; this skill decides which resource fits and how it is scoped and reused.

Recommended Workflow

1. Inventory the values the flow needs: derived, cached, shared, per-element.
2. Choose resource type per the table above.
3. Name with a prefix that encodes scope and type (e.g. v_ variable, c_ constant, f_ formula, col_ collection, tt_ text template).
4. Initialize SObject variables defensively (check null before dot-access).
5. Prefer formulas over "assignment chains" for derived values.
6. Avoid "magic number" literals in element fields — promote to Constants.
7. Document non-obvious formulas with a Description.

Review Checklist

• [ ] No duplicated literals — promoted to Constants
• [ ] Derived values computed by Formulas, not Assignments
• [ ] Collection variables typed correctly (SObject vs primitive)
• [ ] SObject field references null-guarded
• [ ] Naming prefix convention applied
• [ ] Description filled on every non-trivial resource

Salesforce-Specific Gotchas

1. Collection variables do not deduplicate. Adding the same record twice leaves two entries; loops see both.
2. Formulas recompute every reference. Heavy formulas referenced inside a loop multiply cost — cache in an Assignment if recompute is expensive.
3. Formula return types cannot be changed after saving without errors in downstream references. Plan the return type upfront.
4. {!$Record} changes meaning in scheduled paths after a DML in the same transaction — the in-memory record does not reflect mid-transaction updates.
5. Text Template merge fields do not HTML-escape by default in rich-text mode — user-entered text can break layout or inject markup. Use plain-text mode or strip HTML before inclusion.
6. Choice labels and values are both strings — a numeric-looking choice value is still text and must be Converted before numeric comparison.

Output Artifacts

Related Skills

• flow/flow-cross-object-updates — uses collections to bulkify DML
• flow/flow-element-naming-conventions — naming conventions for elements and resources
• admin/custom-metadata-types — externalize flow configuration

Package files

• references/examples.md
• references/gotchas.md
• references/llm-anti-patterns.md
• references/well-architected.md
• templates/flow-resource-patterns-template.md
• scripts/check_flow_resource_patterns.py