Conditional mapping

Choosing a target value from source conditions, and keeping the condition readable six months later. The second half is the lesson. The mechanics are simple: a condition, a value when true, a value when false. The difficulty is that conditional logic accumulates — one rule becomes three, three become a nested expression nobody can unpick, and the business rule inside it becomes invisible. THREE HABITS THAT KEEP IT READABLE. ONE: write the rule in words in the mapping specification FIRST, then implement it. If the sentence is hard to write, the expression will be worse. TWO: prefer a LOOKUP over a chain of conditions where the rule is really a translation table — Lesson 9, and it moves the rule somewhere a business user can see and change. THREE: never nest more than two levels deep in one expression. Beyond that the logic belongs in a lookup, in a separate…

In this module: Module 5 · Mappings and transformations

1. 1What a mapping really isFree preview
2. 2The mapper, practically
3. 3Required, optional and the empty element
4. 4Repeating elements and loops
5. 5Conditional mapping
6. 6Functions: strings, numbers and dates
7. 7Dates and time zones, carefully
8. 8Numbers, precision and currency
9. 9Lookups inside a mapping
10. 10Testing a mapping with real data
11. 11Namespaces, and the errors they cause
12. 12Keeping a mapping maintainable
13. 13What breaks: five mapping failures
14. 14Lab briefing · Map two schemas that disagree