A Guide to Generating Swift Code with Swift Mustache (Part 1)
Article Summary
Esraa Eid from Deloitte UK reveals how to make Swift code generate Swift code—no low-level languages required. She explores three powerful approaches to transform JSON schemas into production-ready Swift structs.
This hands-on guide walks through generating Swift code programmatically using Swift Mustache, a logic-less templating engine. The article includes a complete working example with code samples, showing how to transform JSON Schema specifications into Swift structs with support for optionals, arrays, and Codable conformance.
Key Takeaways
- Swift Mustache uses templates plus data to generate code without complex logic
- Complete implementation generates User struct with optionals and arrays from JSON Schema
- Template approach separates code generation logic from core codebase for maintainability
- Mustache works across multiple languages: JavaScript, Python, Ruby, Java, and PHP
- Challenges include limited debugging info and learning curve for complex code generation
Swift Mustache provides a flexible, template-based approach to generate Swift structs from JSON schemas, though it requires learning Mustache syntax and lacks robust debugging for complex scenarios.
About This Article
Esraa Eid needed to convert JSON Schema specifications into Swift structs. The challenge was keeping type safety and Codable conformance intact while handling optional fields, arrays, and nested properties without writing code manually.
She built Swift Mustache templates with conditional logic using {{#isArray}}, {{#isOptional}}, and section tags. These templates automatically generate struct definitions from JSON Schema data. The reusable template files keep generation logic separate from the main codebase.
The template approach made it possible to write files that produce production-ready Swift code, like struct User: Codable with correct type annotations. Mustache syntax handles custom inheritance, loops, and encoding/decoding, so you don't need deep language knowledge to use it.