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The same plain-backtick "See sample: \`x.good.al\`." form fixed on al-methods-limited-during-write-transactions (PR #161) turned up repo-wide on 15 more of this PR's articles - Knowledge-Retrieval.ps1 requires the markdown-link form to associate a sample with its article. All 16 fixed; the four local validators (frontmatter, knowledge-index, knowledge-retrieval, review-fixtures, skill-index) pass.
28 lines
1.8 KiB
Markdown
28 lines
1.8 KiB
Markdown
---
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bc-version: [all]
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domain: style
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keywords: [boolean, option, yes-no, magic-number, variable-typing, field-typing]
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technologies: [al]
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countries: [w1]
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application-area: [all]
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---
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# Binary yes/no choices must be typed as Boolean, not Option or Integer
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> Contributions welcome — open a PR to refine or extend this article.
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## Description
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When a field or variable represents a genuine true/false state — yes/no, on/off, active/inactive, blocked/not blocked — it should be typed `Boolean`. Modeling that same predicate as an `Option`/`Enum` with two members, or as an `Integer` with two magic-number values, adds a layer of indirection a reader has to resolve before understanding the code. This is about semantics, not member count: a domain concept that currently has exactly two named alternatives — Inbound/Outbound, Debit/Credit, Buy/Sell — is not automatically a Boolean in disguise. An `Enum` can be the clearer model there, including when it needs to implement an interface, preserve an existing contract, or leave room for a future third value. The distinction is whether the domain is genuinely a stable predicate, not how many states it currently has.
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## Best Practice
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Type a field or variable as `Boolean` when the domain concept is inherently a true/false state. Do not replace a meaningful two-option domain model with a Boolean solely because it currently has two values.
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See sample: [`binary-choice-must-be-boolean.good.al`](binary-choice-must-be-boolean.good.al).
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## Anti Pattern
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Modeling a yes/no choice as an `Option` with two members, or as an `Integer` with magic-number values, forces every caller to remember which value means what and leaves room for a meaningless third value.
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See sample: [`binary-choice-must-be-boolean.bad.al`](binary-choice-must-be-boolean.bad.al).
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