Braces Off, Lowercase On

Braces Off, Lowercase On

A partner's ordering API identifies every record by its Business Central SystemId, and it is picky about the spelling: ids must travel as ea48a3e0-48e0-4ab7-b1a1-e3ea85bf1b75 — lowercase, hyphens kept, no braces — and they come back in exactly that shape. The helper your predecessor wrote sends Format(Id), which is {EA48A3E0-48E0-4AB7-B1A1-E3EA85BF1B75}, so the partner rejects every call; and the first malformed id the partner ever sent back crashed the whole import with an Evaluate error. You will rewrite both directions.

Requirements

Create a codeunit named "Api Id Format" with two public procedures:

procedure ToApiId(Id: Guid): Text
procedure TryParseId(Input: Text; var Id: Guid): Boolean

Rules:

1. ToApiId returns the id as 32 lowercase hexadecimal digits in five hyphenated groups of 8-4-4-4-12 — 36 characters, no braces: the GUID {EA48A3E0-48E0-4AB7-B1A1-E3EA85BF1B75} comes out as ea48a3e0-48e0-4ab7-b1a1-e3ea85bf1b75.
2. The all-zero GUID (the null GUID — the value an unassigned Guid variable holds) means "no id": ToApiId returns an empty text for it, never 00000000-0000-0000-0000-000000000000.
3. TryParseId accepts both the API form (ea48a3e0-48e0-4ab7-b1a1-e3ea85bf1b75) and Business Central's braced display form ({EA48A3E0-48E0-4AB7-B1A1-E3EA85BF1B75}), stores the value in Id, and returns true. Upper- and lowercase hex digits are accepted in either form.
4. TryParseId returns false for text that is not a GUID — empty text, words, a truncated id, or something GUID-shaped whose characters are not hex digits. TryParseId must never raise an error, whatever the text contains.
5. The all-zero GUID spelled out as text (00000000-0000-0000-0000-000000000000) is "no id" too: TryParseId returns false for it.
6. Round trip: for any non-null GUID, TryParseId accepts the text ToApiId produced and yields exactly the original value.
7. After a false, the returned Boolean is the only graded signal — whatever is left in Id is not checked.

Pick object IDs in the 50100–50199 range and reference other objects by name, never by ID.

What to know

Format(Id) gives the display form — braces and uppercase. The three-argument Format(Value, Length, FormatNumber) selects one of the standard formats instead, and the GUID row of the standard-formats table on Learn shows what each number produces: formats 0 to 2 are the braced form, format 3 is the 32 digits with no hyphens at all, and format 4 is the hyphenated form without braces. Every one of them is uppercase — lowercasing is a separate step.

Evaluate(Id, Input) is the parser, and it understands both the braced and the bare spelling. Used as a statement, it raises an error when the text is not a GUID; captured as a Boolean expression, it reports the failure as false instead — that difference is what caused the crash. The all-zero GUID is perfectly acceptable text to Evaluate, so rejecting it afterwards is your job.

The starter checks for "no id" by comparing the Guid with an empty text. That compiles, because AL converts between the two types, but a GUID is never text: its empty value is the all-zero GUID, and IsNullGuid is the check that names that fact. Replace the comparison rather than reasoning about what the runtime makes of it.

What the tests check

ToApiId is compared character for character against the expected text for a fixed GUID and for a freshly generated one (whose expected text the test computes on its own, so hardcoding the example fails), asserted to differ from Format(Id) for a generated GUID, and expected to return an empty text for the null GUID. TryParseId is fed the bare lowercase form, the bare uppercase form, the braced uppercase form and the braced lowercase form (each must return true and yield the GUID it spells), then garbage — not-an-id-at-all, a truncated id, zzzzzzzz-zzzz-zzzz-zzzz-zzzzzzzzzzzz, and empty text — plus the all-zero GUID text (each must return false, not an error). One round-trip test runs ToApiId and then TryParseId on a generated GUID and expects the original value back.

Learn More

• Formatting values, dates, and time — the standard GUID formats table: what each format number produces.
• Guid data type — the text spellings a GUID accepts, with Format and Evaluate as the conversions.
• System.Evaluate method — the optional Boolean return that turns a parse failure into false.
• System.IsNullGuid method — the check for the all-zero GUID.